Show

SI Tutorial, Phase 1 - Building a Single

Cylinder ModelStep 1 - Starting WaveBuild, Setting General Parameters, and Creating aSimulation TitleIn this step we will open WaveBuild and establish some preliminary settings that are important forevery simulation.

1.1 Starting WaveBuild

Type wb at the command prompt

Once the application opens, the WaveBuild GUI should have a blank canvas and appear as in Figure1.

Figure 1: WaveBuild window at startup

The title bar is across the top of the WaveBuild GUI window. It lists the name of the currently openfile (NoName.wvm by default, until renamed). If changes have been made to the file and haven't yetbeen saved, an asterisk (*) will appear next to the filename. See Figures 2 and 3.

Figure 2: Title bar when WaveBuild application first opens

Figure 3: Title bar with unsaved changes to the model

The pull-down menus are listed across the top of the GUI, beneath the title bar (see Figure4). Clicking these with the left mouse button will open up menus with selection items.Linux/UNIX users: The Help pull-down menu will appear at the far right side of the window.

Figure 4: Pull-down menu

The toolbar contains shortcut buttons for frequently performed operations.

New

Executes the File > New... function.

Open

Executes the File > Open... function.

Save

Executes the File > Save function.

Undo

Executes the Edit > Undo function.

Redo

Executes the Edit > Redo function.

Find

Executes the Edit > Find function.

Select

Puts the cursor in select mode.

Place Element

Puts the cursor in element placement mode, which places an

instance of the element selected in the Elements Tab for everymouse click on the canvas.

Cut

Executes the Edit > Cut function.

Copy

Executes the Edit > Copy function.

Paste

Executes the Edit > Paste function.

Constants Table

Executes the Simulation > Constants > Table function.

Run Input Check

Executes the Run > WAVE > Input Check function.

Run Screen Mode

Executes the Run > WAVE > Screen Mode function.

Run Batch Mode

Executes the Run > WAVE > Batch Mode function.

WavePost

Executes the Run > WavePost function.

WNOISE

Executes the Run > WNOISE function.

Text Editor

Opens the Text Editor specified in the Tools > Options tab.

Favorite Application

Opens the Favorite Application specified in the Tools > Options

tab.

The canvas is the main portion of the WaveBuild window and where the flow network will beassembled and described (see Figure 5).The canvas is a customizable surface. You can customize the properties for the WaveBuild canvasby selecting the Canvas Properties... option from the Edit pull-down menu or by right-clicking on thecanvas background and selecting the Edit Canvas Properties... context menu item. Customizableoptions include canvas size, annotation display, and grid appearance.

Figure 6: How to Edit the Canvas Properties

Figure 5: The WaveBuild canvas

The Case Manager is at the bottom of the

canvas. The and buttons allow you to theadd and delete cases while the arrow buttonsallow you to navigate between existing cases(first case , previous case , next case , lastcase ).Thetextfieldtellsyouexactlywhich case you are in and how many cases there are in total. You can type directly into the text fieldand press enter to jump to a specific case. In any case other than Case 1, the background of the textfield turns red as a reminder that you are not in Case 1. Switch back to Case 1 if you wish to makeany changes to the model geometry. The Run checkbox allows you to select whether or not WAVEshould execute the current case in the simulation. By default, the checkbox is checked for all newcases.

1.2 Setting General Parameters

With any new model, the first step should always be to define the general parameters for thesimulation, specifically the units system to initialize all data entry. Open the General ParametersPanel by selecting General Parameters... under the Simulation pull-down menu.For this tutorial, all units will be defined in the SI system with mm as the basic unit of length. Select SI[mm] from the Units option menu. Wherever an input is required in WaveBuild, the units for thatinput will be displayed next to the entry field. When a numeric input is provided, if it is in another unitthan the initialized unit, the user can change the units for entry. Changing the selection in this optionmenu at a later point will not convert previously-entered values between units systems!Under the Start Options section of the panel, note the toggle button next to Reinitialize FlowfieldBetween Cases. Turning this on will cause WAVE to start from the user-imposed initial conditions forwall temperatures, gas temperatures, pressures, velocities, and species concentrations in everysubsequent case when multiple cases are defined (Case #1 is unaffected by this setting). This optionis turned off by default because in most instances the final conditions for a converged case are closerto the final conditions of the following case than the user-imposed initial conditions. Assuming this istrue, each case will converge to the final solution quicker. For this tutorial, the toggle button shouldremain off.In the General Parameters section of the panel, type 30 in the Simulation Duration text field. Wewill be simulating an engine and this number will define the number of engine cycles tosimulate. Since we don't know how many cycles our simulation will take to converge, we will set atypical number for a gasoline engine and note the convergence behavior at run time. If our number ishigher than required, auto-convergence will stop the simulation.Note that the background of the Simulation Duration field turns yellow. This is because the units arelisted as s for seconds and 30 seconds far exceeds the recommended value for simulation duration inthe intelligent defaults settings. WAVE, by its nature, simulates fluid flow using a timebase ofseconds. When a cyclic process is introduced to the simulation (such as an engine cylinder, anoscillating flow source, etc.) WaveBuild knows to change to a cyclic timebase. Once we place theengine cylinders on the canvas, this units field will automatically change to cycles and the backgroundof the text field will change to white. "Behind the scenes" the WAVE solver will still be solvingeverything in a seconds timebase, but user entry fields are changed to cycles for convenience.Under the Fuel and Air Properties section of the panel, click on the file tag buttonto open theFuel Property Tag Selector and double-click on INDOLENE (see Figure 7). This will automatically fillin the word INDOLENE in the text field. Similarly, typing in the word directly into the field indicatesthe use of a tag. To specify a particular file not aliased in the tags file, use the file browserbuttonto open a file browsing window and select the properties file to use. This will fill the textfield with an absolute file reference, using pointed brackets, <>, to surround the entry, denoting afilename.

Figure 7: Selecting the INDOLENE tag

In WAVE, five species are used and transported throughout the model. These are Fresh Air,Vaporized Fuel, Burned Air, Burned Fuel, and Liquid Fuel; numbered Species 1 to 5 respectively. Allproperties for these species are defined in a single properties file (with a .fue extension) thatcontains information on how the fuel and air react at different temperatures, pressures, and

concentrations. The appropriate properties file should be selected for the fuel being used in themodel. For simulations using only air, any properties file may be specified since all containinformation on the properties of air. Ricardo ships numerous pre-made properties files and all areselectable from the default tags list. The user can create their own file if desired by clicking onthe Create Properties File button to use the pre-processor.

Note the End of Cycle Angle text field. This field is used to specify the crank angle that WAVE willuse to denote the start/end of subsequent engine cycles. By default (setting of auto), WAVE usesthe IVC of cylinder #1 as the end of cycle. This is acceptable for almost all engine simulations exceptwhen VVT is employed and continuity between cases is important. In that case, a crank angle can bespecified and should be just after the latest IVC for cylinder #1 in the simulation. For this tutorial, thedefault setting of auto is appropriate.When finished, the General Parameters should appear as in Figure 8.

Figure 8: Completed General Parameters Panel

Click on the Convergence tab. This tab allows the user to activate the auto-convergencemechanism, which tells WAVE to end the simulation if it converges to within the specified tolerancevalue for the specified number of consecutive cycles (default of 1% for 1 cycle) regardless of whetheror not it has reached the specified duration. Turning this option off will cause WAVE to run to the fullspecified duration for each case in the simulation.For all simulations, velocity (U) and pressure (P) are checked for convergence in every computationalcell in the last timestep of each cycle. In simulations where WAVE's structural conduction model isimplemented, the calculated wall temperature (T) is also checked for convergence. In simulationswhere WAVE's control systems are used, PID controller tolerances are also included in theconvergence calculation. Finally, the user has the option of adding any cycle-averaged quantitiesdesired to be included as additional criteria.

For this tutorial, the toggle button should remain on and the default values are acceptable. Whenfinished, the Convergence tab should appear as in Figure 9.

Figure 9: Convergence Tab

Press the OK button to close the General Parameters Panel and save the settings.

1.3 Creating a Simulation Title

Add a Title to the file by selecting Title... from the Simulation pull-down menu. The Title Panel willpop up for you to enter a text string that will serve as the simulation title. This title will be printed tothe output file by WAVE at runtime so it is convenient to give the model a descriptive name for laterreference. It can be up to 120 characters long and may include any alphanumeric characters orsymbols with the exception of curly brackets, { }. Constants (discussed in Step 4 of this tutorial) andoperations on constants may be used and will be evaluated when placed inside curly brackets, {}.Pre-definedWAVEconstantsareconvenienttousesometimesandinclude $file,$case, $subcase, $fullcase, $version, and $date. Also useful are user-definedconstants that control important parameters such as engine speed and load. Type SI Tutorial, 4Cylinder Gasoline Engine at {SPEED} rpm in the Title text field and click on the OK button to applythe title (the constant SPEED will be defined in Step 4). The simulation title appears centered acrossthe top of the WaveBuild canvas and is fixed in this location. When finished, the WaveBuild canvasshould appear as in Figure 10, below.

Figure 10: WaveBuild canvas with Simulation Title

Save your model

Click on the Save button in the toolbar

to save the file.

The first time the file is saved, you will be prompted for a filename and directory where the file will bewritten (the file is saved with a .wvm extension, for "WAVE model"). You will also be prompted to addcomments for the file (this option can be deactivated via the File tab on the Options Panel locatedunder the Tools... pull-down menu). When the save button is subsequently clicked, or if the file is nota newly created file (opened from a pre-existing file), the currently open file will be overwritten. Tosave the file elsewhere or with a different name, select the Save As... option from the File pull-downmenu. Save this file with a descriptive name, such as tut_si1.wvm.

Proceed to Step 2 - Building the Flow Network on the WaveBuild Canvas

Show

SI Tutorial, Phase 1 - Building a Single

Cylinder ModelStep 2 - Building the Flow Network on the WaveBuild CanvasIn this step we will layout the junction and duct entities that are required for the single cylinder modelon the WaveBuild canvas.

Chapter sections

Example Input File:

.\examples\engine\TUT_si\tut_si1.wvm

2.1 Placing Required Junctions

2.2 Connecting the Junctions withDucts

Example Output File:

.\examples\engine\TUT_si\tut_si1.wps

2.1 Placing Required Junctions

The basic geometry of the system we will model in this phase is shown in Figure 1. In order to modelthis, we will have to represent both the intake port and exhaust port using two duct elements, one forthe tapered section and one for the un-tapered section. We will use simple orifice elements toconnect the two ducts (one orifice on each side of the cylinder). The open ends of the ports will berepresented using standard ambient elements.

Figure 1: Single Cylinder Layout Sketch

Move the mouse over the Ambient junction icon listed in theElements Tree. Hold down the left mouse button and drag itonto the WaveBuild Canvas, dropping it anywhere. This willplace one junction of the simple ambient type onto the modelcanvas (see the WaveBuild HELP on how to work with theElements Tab). To place additional junctions withoutcontinually dragging and dropping, click on the placeelement + button in the toolbar across the top of the WaveBuildGUI. The mouse pointer changes to a "+" sign when themouse is moved over the WaveBuild canvas.The mouse pointer is now in junction placement mode. Injunction placement mode, a junction of the selected type will be placed on the canvas every time youpress any mouse button. The mouse will remain in junction placement mode until you click on theSelect button on the toolbar across the top of the WaveBuild GUI or hit the Esc key to return toselect mode, at which point the mouse pointer will return to appearing as an arrow when moved overthe canvas.

Place two of the Ambient junctions on the canvas approximately 12 grid squares aparthorizontally. Note that when placed on the canvas, junctions "snap" to the nearest grid intersectionpoint. This behavior can be modified via the Edit > Canvas Properties... menu item.Drag and drop two Orifice elements from the Elements Tree on the canvas between the ambientjunctions. Finally, drag and drop an Engine Cylinder elementfrom the Elements Tree between theOrifice junctions. When finished the WaveBuild canvas should appear as in Figure 2.

Figure 2: Junctions placed on the canvas

2.2 Connecting the Junctions with Ducts

Now that all of the junctions required for the single cylinder model have been placed on the canvas,ducts must be created to connect the junctions together. Using the left mouse button, click and dragfrom the pink connection point on the leftmost ambient junction, labeled amb1 in Figure 2, to the leftconnection point on the neighboring orifice junction, labeled orif1 in Figure 2. This draws/creates aduct between the two junctions. The leftmost ambient will be the intake ambient and the rightmost willbe the exhaust ambient. Connect the remaining junctions following the Left to Rightconvention (remember, the Left to Right convention doesn't necessarily mean Left to Right on thescreen, it is merely a coincidence in this case!). When finished, the canvas should appear asin Figure 3.NOTE: The ducts connecting the junctions appear as yellow lines. This is an indication thatsome geometric property of the ducts (i.e. diameter) has not been properly defined. Also, as youconnect the two ports of an orifice junction, the icon of the orifice disappears because the ductsconnected on both sides have default diameter values of 0 (zero) at this point. The orifice icondynamically adjusts its appearance to reflect any step change in duct diameters. After you enter theduct properties in Step 3, the orifice icon will "automagically" appear again and the ducts will turnblack!

Figure 3: Ducts connecting Junctions on Canvas

Save your model

Click on the Save button in the toolbar

to save the file.

This overwrites the .wvm file with the new information and backs up the previous .wvm file to a filewith the extension .wvm_bak1. WaveBuild will create up to 9 backup files with the .bak extension,all of which can be opened and viewed using WaveBuild.

Proceed to Step 3 - Defining Ambients, Ducts, and Orifices

Show

SI Tutorial, Phase 1 - Building a Single

Cylinder ModelStep 3 - Defining Ambients, Ducts, and OrificesIn this step we will select all of the elements (ducts and junctions) on the WaveBuild canvas, anddefine their geometric values and initial/boundary conditions.

Example Input File:

3.1 Defining Ambients

With the general parameters defined (specifically a units system) and all of the relevant ducts andjunctions placed on the canvas, it is time to define the geometric characteristics of the model as wellas specify the initial conditions and boundary conditions.We will start by defining the Ambient junctions. As stated earlier, the left-most Ambient junction willbe the intake ambient. Double-click with the left mouse button on the left-most ambient junction. Thiswill open the Ambient Panel. In the Ambient Panel, the user can specify the conditions of the ambientatmosphere (Pressure, Temperature, and Species Concentrations) as well as specify the propertiesof the orifice at the end of the attached duct.Temperature and Pressure fields on the Ambient tab and all inputs on the Initial FluidComposition tab are used to specify the fluid conditions of the atmosphere around the attachedduct. The default values of 1.0 [bar] and 300[K] and a composition of 100% fresh air are suitable forthis simulation and don't need to be changed. In some simulations, the user may choose todramatically change the temperature and pressure and/or adjust the composition to model aboundary that is either not atmospheric, like the outlet of a compressor or inlet of a turbine, or is not atsea level, such as an engine operating at high altitude.The Diameter, Discharge Coefficient, and Acoustic End Correction fields are used to model theorifice created where the duct ends at the ambient. The Diameter field has a default value of AUTO toassume the same diameter as the attached duct (no restriction created). The Discharge Coefficientcan be set to AUTO to have WAVE calculate this value internally during the simulation. This is onlyapplied to flow going from the Ambient into the attached duct and should be a value between 0 and 1if specified. The Acoustic End Correction is only used for acoustic simulations and is discussed indetail in the Acoustics Manual.The ambient's diameter value can never be larger than the diameter of the attached duct as itwould have no physical meaning, however a value of 0 (zero) makes the ambient junction behavelike a closed end to the attached duct (an end-cap).The selection of Fixed or Floating Solution Type is discussed in detail in the Acoustics tutorials. Thedefault setting of Floating is appropriate in almost all cases and should not be changed.For this simulation, the default values are all appropriate and we only need to change the name of thejunction. Type Intake in the ID text field (name for the junction as displayed on the canvas and in theoutput files). When finished, the Ambient Panel should appear as in Figure 1, below. Do the samefor the right-most ambient junction and type Exhaust in the ID text field.

Figure 1: The Ambient Panel for the Intake

3.2 Defining Ducts

Next we will define the ducts. Assume that all the geometric data for the system has been measuredand recorded and that a labeled sketch is provided as in Figure 2. Minimally, a duct is definedby Left and Right Diameters,Length, Discretization, and Initial Conditions.

Figure 2: Single Cylinder Layout Sketch

Double-click with the left mouse button on the duct labeled duct1 to open the Duct Panel. Across thetop of the Duct Panel is the Duct ID (name for the duct as displayed on the canvas and in the outputfiles) and, in the Connectivity section, the junctions connected to the duct's Left and Right ends arelisted.

The middle of the Duct Panel is the Schematic section which will update the drawing of the duct toreflect the entered geometric dimensions (Bend Angle is not drawn in the schematic as it has nophysical meaning in a 1-D model, it is simply used to calculate a pressure loss based on the angleand bend radius). Fuel Injectors, Spray Impingement Points, and Thermocouples will also appear inthe schematic if present in the duct.The bottom of the Duct Panel is reserved for two layers of tabs which hold entry fields in which theuser will specify all information relevant to that duct. Of all of those tabs, there are three of primaryimportance that we will use in this tutorial. Under the top level tab of Duct Data, the Dimensions tab,the Coefficients tab, and the Initial Conditions tab are particularly relevant in all ducts and are theonly tabs we will be editing during the course of this tutorial (see Figure 3).

Figure 3: Required Duct Data Tabs

On the Dimensions tab, with the Shape selected as Circular, type the dimensions givenfor duct1 in Figure 2 into the appropriate entry fields (Left and Right Diameters and OverallLength). The engine bore for this example is 78.1 [mm] so, following the general recommendationfor discretizing the model for performance simulation, set the Discretization Length to 35 [mm] (clickhere to read a sidebar on Discretization). When completed, theDimensions tab for duct1 shouldappear as in Figure 4.

Figure 4: Duct Panel Dimensions Tab for duct1

On the Coefficients tab, type 0 (zero) in the Friction and 1.5 in the Heat Transfer coefficient fieldsunder the Coefficients section of the tab (click here to read a sidebar on Port Flow Testing tounderstand why). The default setting of 0.0 for the Pressure Loss Coefficient is suitable for thissimulation. The Left and Right end Discharge Coefficients will be automatically calculated byWAVE when left as auto based on the diameter of the duct at the relevant end and the diameter ofthe neighboring duct/orifice. If desired, this can be overridden by typing in a value for the DischargeCoefficient from 0.0 to 1.0. For the purpose of this tutorial, the default value of auto is suitable andshould not be changed. When finished, the Coefficients tab should appear as in Figure 5.

Note that the Friction and Heat Transfer Coefficients have default values of 1.0. These valuesare multipliers for the standard calculation. Thus values of 0.0 imply that there is no pressureloss due to friction and no heat transfer occurring along the length of the duct while values of 2.0imply that twice the standard pressure loss due to friction and twice the standard heat transfer isoccurring. These multipliers may be used as "tuning knobs" to adjust friction and heat transferand should be changed according to the surface roughness of the material and flow conditions inthe duct. Keep in mind that surface roughness will affect BOTH of these parameters and thatpressure loss due to increased heat transfer can be much greater (expansion/contraction of thegas) than pressure loss due to friction!

Figure 5: Duct Panel Coefficients Tab for duct1

On the Initial Conditions tab, type the conditions given for duct1 in Figure 2 into the appropriateentry fields (Pressure, Temperature, and Wall Temperature). In the case of duct1, all of the defaultsettings are correct for our model. When finished, the Initial Conditions tab should appear asin Figure 6. Note that initial conditions of Pressure and Temperature need not be extremely accurate in anengine simulation as the gas will quickly move through the system and conditions will be recalculated frequently. The initial conditions as set will be flushed out within the first few enginecycles of the simulation. Default settings of 1.0 [bar] and 300 [K] are appropriate for most engine

simulations. Turbo/Supercharged simulations should have more appropriately set conditions to

reflect the "boosted" state of the fluid and avoid start-up calculation errors. Note that if the Structural Conduction model (discussed in later tutorials) is not active for a duct,not only is the Wall Temperature value as entered the initial Wall Temperature, it is also the fixedWall Temperature for the duration of the simulation! Thus, special attention should be paid tosetting Wall Temperatures throughout the model to ensure that heat transfer is accounted forappropriately, especially in the exhaust system. If reliable wall temperature data is not available,the Structural Conduction model should be activated and the wall temperature will be calculatedduring the simulation to give reasonable results.Click the OK button to close the Duct Panel for duct1. As above, edit duct2, duct3, and duct4 andenter the relevant information according to the schematic shown in Figure 2. Usea Discretization length of 35 [mm] on the intake and 40 [mm] on the exhaust. Make sure to setthe Friction coefficient to 0 (zero) and the Heat Transfer coefficient to 1.5 for each duct and do notenter Bend Angles for duct2 and duct3!

Figure 6: Duct Panel Initial Conditions Tab for duct1

3.3 Defining Orifices

When all of the ducts have been defined, note on the WaveBuild canvas that the orifice junctionshave reappeared. Since the ducts all have matching diameters at the ends where they are joined byorifice junctions, the junctions appear with a straight, smooth line across both the top and bottom.To demonstrate the altering appearance of the orifice junction, edit duct1 to have a Right Diameter of50 [mm]. Note the orifice junction changes in appearance to illustrate the step change from a largerto a smaller diameter duct.

Click the Undo button in the toolbar

to return the Right Diameter of duct1 to 35 [mm] again.

Now double-click on the orif1 junction and note the only editable fields for an orifice junction are theID of that junction and the junction Diameter (diameter of the orifice plate) if one exists. If an orificejunction is simply used to join two duct ends together, than the default setting of auto issufficient. The auto setting implies that the diameter of the orifice is equal to that of the smaller of thetwo attached ducts. If a restriction is to be modeled, a Diameter smaller than the smallest of the twoattached ducts should be used. Type 20 [mm] in the Diameter text field and hit the OK button. Notethe orif1 junction now appears as if an orifice plate is reducing the diameter at the junction.Click the Undo button in the toolbarto return the Junction Diameter to auto again. For thistutorial all orifice junctions will have a Diameter of auto unless otherwise specified.

Orifice with no change

of area

Orifice with contraction

Orifice with restriction

An orifice diameter can never be larger than the diameter of the smallest attached duct as it wouldhave no physical meaning, however a value of 0 (zero) makes the junction behave like a closedseal between the attached ducts.When completed, the WaveBuild canvas should appear as in Figure 7.

Figure 7: Completed WaveBuild Canvas

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Step 4 - Defining the Engine

Show

SI Tutorial, Phase 1 - Building a Single

Cylinder ModelStep 4 - Defining the EngineIn this step we will input all of the required data for the engine. The Engine currently is not an entityon the canvas. It physically would consist of all engine cylinders represented on the WaveBuildcanvas (currently only one) but also includes physical sub-models for combustion, friction, heattransfer, etc.

Example Input File:

4.4 The Combustion Tab

4.1 The Geometry Tab

To define the engine, open the Engine General Panel by selecting Engine... from the Model pulldown menu. The Engine General Panel consists of numerous tabs, each used to define thecharacteristics of the engine or the physical sub-models associated with the engine.

There are four primary tabs that are important for every engine. These are Geometry, OperatingParameters, Heat Transfer, and Combustion.

Onthe Geometry tab,underthe Configuration section enter therelevant data for this engine as shownin Table 1.The No.ofCylinders fielddoes not automatically update whencylinders are placed on the screen(this allows for definition of the enginebefore the model is built). The usermust enter the correct number ofengine cylinders manually.The Strokes per Cycle field is usedto define the engine as a 2-stroke or4-stroke engine (optionally a 6- or 8stroke engine for research purposes).The Engine Type field is used toenable different combustion andemission models when either SI orDiesel are selected. The Motoredoption allows for engine motoringsimulation (engine pumping only, nocombustion via cancelling all injectionevents).Onthe Geometry tab,underthe FrictionCorrelation sectionenter the relevant data for this engineas shown in Table 2.These coefficients are used in theChen-Flynn friction correlation model.This model is used to calculate theFMEP(Friction Mean Effective Pressure) forthe engine. When data is collected inthe test cell, it can be plotted andcorrelated using the Chen-Flynnmodel so that FMEP may becalculated at non-tested enginespeed/load conditions. The equationto calculate FMEP in WAVE is:

No. of Cylinders

Strokes per Cycle

Engine Type

Spark Ignition

Bore

78.1 [mm]

Stroke

82.0 [mm]

Connecting Rod Length

Wrist Pin Offset

Compression Ratio

150.0 [mm]0.0 [mm]

10.02 [mm]

Clearance Height

Table 1: Data to be entered in the Configuration fields

ACF

0.35 [bar]

BCF

0.005

CCF

400 [Pa/min*m]

QCF

0.2 [Pa/min2*m2]

Table 2: Data to be entered in the Friction

Correlation fields

FMEP = ACF + BCF(Pmax) + CCF(rpm

* stroke/2) + QCF(rpm * stroke/2)2The use of the BCF term is to account for changes in Pmax, which can be used to vary frictional lossesacross a range of engine loads. The CCF and QCF terms are used to account for changes in rpm,varying frictional losses across a range of engine speeds.If the simulation is only to simulate tested speed/load points, the FMEP can be entered directly usingonly the ACF value (directly entering FMEP in the appropriate pressure units) and setting the othercoefficients to 0 (zero).When completed, the Geometry tab should appear as in Figure 1.

Figure 1: The Engine General Panel Geometry tab

4.2 The Operating Parameters Tab

Click the Operating Parameters tab to bring it to the front. In the Engine Speed text field,enter {SPEED} to denote the use of the SPEED constant (also used in the Simulation Title in Step1). This will allow the simulated engine speed to change between cases once we add more casesin Phase 3 of the tutorial. Note that the background of the text entry field turns yellow. This is to warnthe user that the value is outside of the generally acceptable range of values for the EngineSpeed field. Hover over the text {SPEED} and note the tooltip that pops up, stating that theconstant {SPEED} is undefined (Figure 2).To define this constant, open the Constants Panel by clicking on the Constants Panel button in thetoolbaror by selecting Simulation > Constants > Table... from the pull-down menu. Noconstants have yet been defined so the Constants Panel should be blank. Type SPEED under theName column and under the Case 1 column, set a value of 6000. This will correspond tothe {SPEED} value used in the Engine General Panel for Engine Speed in rpm. When completed,the Constants Panel should appear as in Figure 3. Click OK to close the Constants Panel and savethe setting.

Figure 2: The Operating Parameters tab

Figure 3: The Constants Panel

Once the SPEED constant has been defined, the background of the Engine Speed text entry fieldshould turn white to denote an acceptable value. Also note that the simulation title at the top of theWaveBuild canvas has updated to reflect the value of the SPEED constant as given in the title. Hoverthe mouse over the Engine Speed entry in the text field to pop up the tool tip and note that theconstant is now being evaluated correctly as in Figure 4.The Reference Pressure and Reference Temperature fields can be left as their default valuesof 1.0 [bar] and 298 [K] respectively. These values are used in the calculation of volumetric efficiencyfor the engine and may or may not correspond to the ambient conditions of the dynamometer cellwhen tests are performed (different companies use different practices). When completed,the Operating Parameters tab should appear as in Figure 4.

Figure 4: The Operating Parameters tab with SPEED defined

4.3 The Heat Transfer Tab

Click the Heat Transfer tab to bring it to the front. For the standard engine cylinder, there is only onetype of heat transfer model available -- the Woschni correlative model for convective heat transfer(1967). This model assumes simple heat transfer from a confined volume surrounded on all sides bywalls representing the cylinder head, cylinder liner, and piston face areas exposed to the combustionchamber. The area of each is simply calculated from the provided geometry for bore, stroke,connecting rod length, and the added input on this tab for clearance height. Since the piston face andcylinder head are not usually flat slabs of metal, there is a Surface Area Multiplier included for eachto account for domed heads, piston bowls, etc. Multipliers are also provided to increase/decreasetotal heat transfer when the intake valves are open (heating of intake charge affects Volumetric

Efficiency) and when the intake valves are closed (during compression/combustion/exhaust). Addingswirl will increase the total heat transfer due to increased charge motion in the cylinder.Modifications to the standard Woschni model have been added to compensate for varying levels ofIMEP. This can be selected by changing the Woschni Model from Original (1967) to LoadCompensating (1990).For the purpose of this tutorial, enter the relevant data for this engine as shown in Table 3.Woschni Model

Original

Heat Transfer when Intake Valves are Open

1.0

Heat Transfer when Intake Valves are

Closed

1.0

Piston Top Surface Area Multiplier

Cylinder Head Surface Area Multiplier

1.0 (flat-top piston)

1.6 (to make 7665mm2)

Piston Top Temperature

520 [K]

Cylinder Head Temperature

520 [K]

Cylinder Liner Temperature

400 [K]

Intake Valve Temperature

420 [K]

Exhaust Valve Temperature

480 [K]

Swirl Ratio

0.0

Table 3: Data to be entered in the Heat Transfer Tab

When completed, the Heat Transfer tab should appear as in Figure 5.

Figure 5: The Engine General Panel Heat Transfer tab

4.4 The Combustion Tab

Finally, click the Combustion tab to bring it to the front. This panel separates the PrimaryModel choice (required) from the Secondary Model choice (optional, layered on top of the PrimaryModel) and Emissions Models. The general engine cylinder in WAVE simplifies combustion. It doesnot use a predictive combustion model but simply models the heat release caused by combustion vs.time. Since we are modeling a spark ignition engine and selected the Spark Ignition option onthe Geometry tab, we have two combustion models available to use -- the SI Wiebe and Profilemodels.The Profile model is used when Heat Release vs. Crank Angle data is available directly for everyspeed/load point to be tested by the model. This data can be directly entered into WAVE as a tablewith a combustion start time and efficiency.More widely used, however, the SI Wiebe model simply uses an S-curve function that represents thecumulative heat-release in the cylinder. The first derivative of this function is the rate of heatrelease. The SI Wiebe model is very commonly used and represents experimentally observedcombustion heat release quite well for most situations.Select the SI Wiebe option from the Combustion Model drop-down menu. Enter 8.0 [deg] forthe Location of 50% Burn Point and 31.0 [deg] for the Combustion Duration (10-90%). Watch theplot actively update as these values are entered. The default value of 2.0 for the Exponent in WiebeFunction is appropriate for most cases. Change it and watch the shape of the burn curve change aswell. For this example, 2.0 is an appropriate value and should be used. Fraction of Charge toBurn should be left at the default value of 1.0 as well. When completed, the Combustion tab shouldappear as in Figure 6.Click the OK button to save the settings for the Engine General Panel and close it.

Figure 6: The Engine General Panel Combustion tab

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Step 5 - Defining the Intake and Exhaust Valves

Show

SI Tutorial, Phase 1 - Building a Single

Cylinder ModelStep 5 - Defining the Intake and Exhaust ValvesIn this step we will define the intake and exhaust valves by specifying their lift behavior and flowrestriction behavior.

5.1 Defining the Intake Valve Lift

5.1 Defining the Intake Valve Lift Behavior

The connections from duct2 and duct3 to the cyl1 junction are assumed to be valves (all enginecylinder connections are assumed to be valves). The blue connection point to duct2 denotes anintake valve and the red connection point to duct3 denotes an exhaust valve. This is correct for thismodel but is purely coincidental. WaveBuild places engine cylinders on the screen with twoconnections by default. It assumes that the first connection to be used is an intake valve and thesecond connection to be used is an exhaust valve. Any other valves created (by double-clicking onthe cylinder junction and editing the Number of Valves field to be larger than 2) are assumed to beintake valves. This intake/exhaust status can be changed by highlighting the connection of choiceand changing the Type in the drop-down menu (see Figure 1 for example of a modified CylinderPanel). For this tutorial, the two valves created by default are suitable and the number of valvesshould not be changed.Valves are defined globally, for use anywhere in the model. Anywhere a valve is present (on anengine cylinder, in a valve-specific junction, etc.) the user must tell WAVE which globally definedvalve to use. This, for example, allows the user to define an intake valve once and then use it for allengine cylinders.

Figure 1: Adding Valve Connections via the Cylinder Panel

To define a valve, select Valves... from the Model pull-down menu. The Valve List panel will popup. As it is blank, it is clear that no valves have yet been defined. Click on the Add button to create anew valve. This will pop up the Add Valve Panel where the user selects which type of valve touse. The standard valve on an engine cylinder is a Lift valve, selected by default). Clickthe OK button to accept the Lift type and the Lift Valve Editor will automatically appear.

The first entry field under the Valve Parameters

section of the panel is the ReferenceDiameter. This value is typically the inner-seatdiameter (see Figure 2, right), but if the portcoefficient data has been provided in nondimensionalized format, whatever diameter wasused to non-dimensionalize the data should beentered here. For this tutorial, type in aReference Diameter of 35 [mm]. The HeatTransfer Diameter is only required if the valve isan engine valve and the engine conduction submodel is activated for this tutorial, it need notbe entered.

Figure 2: Valve Measurements typically used

Click on the Edit Lift Profile button to open the Valve Lift Profile Editor.

In the Valve Lift Profile Editor, data must be entered for the behavior of the valve. This behavior isdescribed as the lift of the valve vs. time (time is entered as cam or crank angle degrees). There arenumerous options for entering this data including:

Manually entering data into the array

Copying and Pasting an array from MS Excel (on PC platform)

Reading in a pre-formatted external file

Using a tag to alias a pre-formatted external file

INTAKE VALVEDiameterLift Profile

35 [mm]SI1INT tag

Cycle Anchor

330 deg

Profile Anchor

0 [deg]

Duration Multiplier

Lift Multiplier

Lash

Rocker Ratio

Angle Type

Coefficient Profile

1.0

1.414

1.0

Crank

CFTYP tag

For this tutorial the data has already been provided in a

pre-formatted external file that is aliased in thedefault active.tags file. To select this file, click on thetag buttonand select the SI1INT item. Notice thatthe array fills automatically by reading the contents of thefile aliased in the active.tags file and a lift vs. crankangle curve is now plotted on the screen.Some suppliers may provide data for the lift curve incamshaft degrees (the camshaft rotates once for everytwo crankshaft rotations in a 4-stroke engine) so there isa Angle Type pull-down menu to adjust the units onwhich the data is based. Lash, if not alreadyincorporated into the lift array data, should be entered ashot lash. The lash in the system tends to change whenthe engine is running hot and is reduced from the coldlash. Rocker Ratio (if necessary) may be entered aswell.

Table 1: Intake Valve Data

The fields of primary importance are the Anchors and the

Multipliers, located at the bottom of the Valve Lift Profile Editor window. The Anchors allow arbitraryalignment of the valve profile within the engine cycle. The Profile Anchor denotes a point specifiedin the array of angle data. The Cycle Anchor denotes another point in the engine cycle in crankangle degrees. These two points align to locate the valve lift array within the engine cycle. Theseanchors can be parameterized (set as constants) to allow variable valve events between cases (camphasing).The Multipliers are used to multiply every point in the valve array in either lift magnitude or angleduration. These can be parameterized (set as constants) to allow variable valve lift and durationbetween cases. The lift multiplier can also be conveniently used to adjust the units of the text file tothe appropriate units for use in the model (multiply/divide to go from inches to mm, etc.).For this tutorial, enter the following information for valve #1, the intake valve as shown below in Table1. This aligns the 0 degree point in the array data (in Crank Angle degrees) with the330 degree pointin the engine cycle, shifting the valve event over the labeled intake stroke in the plot. It also multipliesall of the lift values by 1.414. When finished, the Valve Lift Profile Editor for valve #1 should appearas in Figure 3, below.

Figure 3: Valve Profile for the Intake Valve

Click the OK button to save these setting and close the Valve Lift Profile Editor.

5.2 Defining Coefficients (Flow vs. Discharge)

The last piece of information required to define a valve is the coefficients. Port coefficients helpdescribe how restricted the flow through the valve is at different lift positions. This data is usuallyobtained through a process of port-flow testing using a steady-state airflow rig. Click on the Edit FlowCoefficient Profiles button to open the Flow Coefficient Profiles Editor.

Similar to the Valve Lift Profile Editor, data must be entered for the coefficients. This behavior isdescribed as values for both the forward and reverse flowing direction (forward implies into thecylinder, reverse implies out of the cylinder) vs. the lift of the valve (non-dimensionalized by dividingthe lift by the reference diameter). Again, there are numerous options for entering this data including:

Manually entering data into the array

Copying and Pasting an array from MS Excel (on PC platform)

Reading in a pre-formatted external file

Using a tag to alias a pre-formatted external file

For this tutorial the data has been provided already in a pre-formatted external file that is aliased inthe default active.tags file. To select this file, click on the tag buttonand selectthe CFTYP option. Notice that the array fills automatically by reading the contents of the file aliasedin the active.tags file and a coefficient profile appears in the plot on the right-hand side of thepanel, see Figure 4.

This file contains information for flow coefficients as we can tell by the fact that at zero lift (zero L/Dvalue) the coefficient has a value of 0 (zero). Flow coefficients must be entered with the first row inthe array being an L/D value of 0 (zero) and forward and reverse coefficient values of 0 (zero).WAVE can also accept discharge coefficients as input. Discharge coefficients are distinguishable bythe fact that the coefficient value at zero lift (zero L/D value) are non-zero. If the first row of the arrayis an L/D value of zero and the forward and reverse coefficients are non-zero, then WAVE assumesthat the array is entered as discharge coefficients. Click on the tag buttonand select CDTYP todisplay a typical discharge coefficient profile, seeFigure 5. These two profiles are derived from thesame data so either will work and is appropriate for this tutorial.Click the OK button to save these setting and close the Profile Editor.Click the OK button on the Lift-Valve Editor panel to save the settings for valve #1 and return to theValve List panel.

Figure 4: Typical Flow Coefficient Profile

Figure 5: Typical Discharge Coefficient Profile

5.3 Defining the Exhaust Valve

Click the Add button again to create a second valve thatwill be used to model the exhaust valve.

Lift Multiplier 1.0

LashFigure 6: The Valves List

Follow the same steps as above but use the following

information for the lift profile (the coefficients can be thesame as the Intake Valve). When finished, the Valve LiftProfile Editor for valve #2 (the exhaust valve) shouldappear as in Figure 7, below.With both the intake valve (valve #1) and exhaust valve(valve #2) defined, the Valves List should appear asin Figure 6. Click the OK button to save these settingand close the Valves List panel.By default, the engine cylinder junction has picked theintake valve connection to use Valve #1 and the exhaustvalve connection to use Valve #2. This is, again,coincidental. On a multi-valve engine it may benecessary to edit the engine cylinder junction andcorrectly specify the valve number to use for eachconnection.

Rocker RatioAngle TypeCoefficient Profile

01.0CrankCFTYP tag

Table 2: Exhaust Values

Figure 7: Profile Editor for Valve #2 (the exhaust valve)

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Step 6 - Adding the Fuel Injector

SI Tutorial, Phase 1 - Building a Single

Cylinder ModelStep 6 - Adding the Fuel InjectorIn this step we will add a fuel injector, connect it to the intake port, and define the required inputparameters.

Example Input File:

6.1 Adding the Injector Element

The single-cylinder model is almost complete all that remains is to add a fuel injector. WAVEhandles fuel injection in one of two primary ways targeting an air-fuel ratio or injecting a specificmass of fuel. The easier of the two methods is to target an air-fuel ratio and let WAVE inject theappropriate amount of fuel based on the airflow. This is the approach used in this tutorial and in avast majority of simulations.Injectors can be added to duct, y-junction, or cylinder elements, but specific injectors can only attachto specific types of flow elements. From the elements tab, drag and drop a Proportional fuel injectorabove duct 2. The proportional type injector can connect to a duct or y-junction flow element, but notcylinder elements. A Proportional injector will always inject enough fuel to the fluid stream to match atargeted air-fuel ratio. This is the simplest type of injector and is very commonly used.To connect the injector to the flow element, click on the injector and drag and drop a connection ontothe duct2 element. This will create a connection line between the two elements (the connection linemust start at the injector element and be dropped onto the duct element, you cannot create aconnection between the two by starting at the duct element). When connected, the model shouldappear as in Figure 1.

Figure 1: Adding an Injector

6.2 Defining the Injector

Now that the injector has been added, we can edit the properties of the injector element. Double clickon the injector element to open the Proportional Injector Panel.On the Operating Point tab, all that needs to be defined is the targeted air-fuel ratio of the injectorwithin the duct. WAVE requires a fuel-air ratio but most frequently air-fuel ratio information isprovided. This is easily overcome by using WAVE's capability to perform simple mathematicaloperations on constants. We will define a constant named A_F and enter air-fuel ratio data in theConstants Panel, but in the text field for Fuel/Air Ratio, type {1/A_F}. This will automatically convertthe air-fuel ratio to a fuel-air ratio as required.On the Position tab, we must define where, along the length of the duct element, the injector injectsfuel into the flow system (if the injector were connected to a y-junction element, this tab would beirrelevant as there is only one fluid cell in a y-junction). Type 25 [mm] into the Distance from LeftEnd text field to move the injector to the middle of the duct (alternatively, click and drag the injectorwith the middle mouse button).On the Properties tab, all that is needed is a temperature for the injected fuel and an amount that willvaporize upon injection into the fluid stream. Type 330 [K] into the Mixture Temperature textfield. Type 0.3 into the Liquid Fraction Evaporated After Injection text field. This field denotes whatfraction of the liquid fuel will immediately vaporize in the fluid stream. The heat required to vaporizethis portion of the liquid fuel is pulled directly from the intake charge, thus cooling it and increasing thedensity (this usually leads to a slight increase in volumetric efficiency). Typical values are 0.2 to 0.3for a gasoline engine.

Click on the Composition tab, where the total composition of the fuel before injection can bespecified. If the aforementioned charge cooling effect is undesirable, then the vapor portion can bespecified here. For this tutorial, the default of 1.0 for Liquid Fuel is suitable and can be left as is(100% of the injected fuel is in liquid state, 20% of that vaporized when injected).When completed, the Proportional Injector Panel should appear as in Figures 2-5, below. Clickthe OK button to close the Proportional Injector Panel and save the data (when prompted to addthe A_F constant to the Constants Panel, select No).

Figure 2: Completed Injector Editor

Figure 3: Completed Position Tab

Figure 4: Completed Properties Tab

Figure 5: Completed Composition Tab

All that remains is to add the A_F constant to the Constants Panel. Open the Constants Panelandtype the constant name, A_F, in the Name column, + row. This will automatically add a new row tothe constant panel. There are no units required and the value of the constant in case 1 should beentered as 14.7 (approximately stoichiometric for the INDOLENE fuel that this simulation isusing). When finished, the Constant Panel should appear as inFigure 6, below.

Figure 6: Adding the A_F Constant

Click the OK button to close the Constants Panel.

The single-cylinder model is complete!

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Phase 2 - Running WAVE and Creating Time Plots in WavePost

SI Tutorial, Phase 2 - Running WAVE and

Creating Time Plots in WavePostRunning the WAVE solver will process all of the information that has been entered into the model andproduce numeric results. These results can be post-processed in WavePost to produce plots andgraphics for reports and presentations.

With these five steps, we will run the WAVE solver and create some output data for postprocessing. WavePost will be used to view plots and cycle-averaged results for the model.

Show

SI Tutorial, Phase 2 - Running WAVE and

Creating Time Plots in WavePostStep 2 - Requesting Time PlotsIn this step we will add requests for plots of specific data to our existing model. Time Plots are plotsof results over the course of a single engine cycle (the last engine cycle in multi-cyclesimulations). Time Plots should be requested whenever the user is aware of specific data they areinterested in analyzing.

2.1 Duct Time Plots

Example Input File:

Suppose we are interested in observing the pressure and temperature at the mid-point of the intakeport during the engine cycle. We can request Time Plots at the intake port (duct2) and WAVE willautomatically create these plots at the end of the simulation. Right-click on duct2 and select the EditPlots... option from the pop-up menu (see Figure 1). The Duct Plot Panel will open with no plots yetdefined at this location. Click on the Create Plot button to open the Duct Plot List.

Figure 1: Adding Plot to duct2

The list of plots available at this location is displayed (this list is context-sensitive and generatedbased on the canvas item selected). Click on the 201 Pressure plot and then, holding the Shiftbutton to multiple-select, click on the202 Temperature plot (most valid duct plots are in the 2xxrange). Click on the OK button to close the Duct Plot List and add these plots to the Existing Plots listin the Duct Plot Panel.The location along the length of the duct from where plots should take their data is specified under theDuct Locations region of the panel. Locations are defined by a normalized value from zero to one(left end of duct is 0, middle of duct is 0.5, right end of duct is 1). Default Locations can be defined forcommonly-used locations to be specified in multiple plots (Default Locations will appear identically forall ducts when the Duct Plot Panel is opened). Custom Locations are specific locations in theselected duct where plots should take their data. Clicking on the Use All Locations button willautomatically create Custom Locations for every cell in a duct. To add locations (either Default orCustom), right-click on the column header and select Insert Column Before or Insert Column After, asappropriate, from the context-menu.Pressure and Temperature are scalar values and, in WAVE, are stored at the center of a given cell(vector values, such as velocity, are stored at cell boundaries). As there is only one cell in duct2, nolocation needs to be specified. The time plots will automatically be created at the 0.5 location (halfway along the duct). Specifying any other location along the length of the duct will create identicalplots.When complete, the Duct Plot Panel should appear as in Figure 2.

Figure 2: Duct Plot Panel with plots at duct2

Click on the OK button to close the Duct Plot Panel. Note the plot icon now hanging off of duct2. Toedit plots at this location again, simply double-click on this icon and the Duct Plot Panel will open.

2.2 Junction Time Plots

Suppose we desired to examine the combustion performance in the power cylinder during the enginecycle. We may want to create a P-V (Pressure vs. Volume) plot. Right-click on the cyl1 junction andselect the Edit Plots...option to open the Junction Plot Panel. The duct plots created above will belisted in the Existing Plots list. Click on the Create Plot button to open the Junction Plot List.Note that there are many more plots in the list than in the Duct Plot List (engine cylinder plots aretypically in the 1xx range). Click on the 111 Linear P-V Diagram and click the OK button to close the

list and add the plot to the Existing Plots list. Also note that an asterisk appears to the right of the plottype for any plot with the currently selected canvas item as a location.No location within the junction needs to be specified for the plot as there is only one calculation pointin a junction. When completed, the Junction Plot Panel should appear as in Figure 3, below. Clickthe OK button to close the Junction Plot Panel.

Figure 3: Junction Plot Panel with plot at cyl1

2.3 System Time Plots

Although there is only one cylinder in our engine, we will eventually be creating a 4-cylinderengine. To observe the behavior of the engine itself (system of cylinders grouped together), click onthe Simulation pull-down menu and select the Time Plot... menu item. This will open the Time PlotPanel where plots can be created for the engine system, as well as sensors, actuators, and pins (tobe discussed in more advanced tutorials).The System Location Type should be active by default when the panel opens. Click on the CreatePlot button to open the Time Plot List for the engine system.A few engine system specific plots are available and even fewer are applicable to our system asmodeled (system plots are typically in the 7xx range). Click on the 701 Engine Torque plot and clickthe OK button to close the list.Again, no location needs to be defined for system plots. When completed, the Time Plot Panelshould appear as in Figure 4. Click the OK button to close the Time Plot Panel. Note, there is nodisplay of the system plot on the canvas as there is not yet a canvas entity to which it can beattached.

Figure 4: Time Plot Panel with system plot of Engine Torque

2.4 Multiple Plots Overlaid

Perhaps we wish to examine the pressure and temperature in the exhaust port and compare it to theconditions in the intake port. We could create separate plots for the duct representing the exhaustport (duct3), but it would be more useful if the data for both ports were on the same plot. Right-clickon duct3 and select the Edit Plots... option from the pop-up menu. Note that the only plots in theExisting Plots list are the pressure and temperature plots from duct2. This is because these plots areallowed at duct3 as well (a P-V plot is not sensible in a duct, nor is engine torque).With plot 201 highlighted, click on the Add Location button to plot the pressure at duct3 on the sameplot as duct2.Do the same for plot 202 to add duct3 to the plot of temperature in duct2. Click on the Use AllLocations button to request the plots at the center of both cells in duct3 (locations of 0.25 and 0.75).When completed, the Duct Plot Panel should appear as in Figure 5.

Figure 5: Duct plot panel with duct2 and duct3 plots overlaid

Click the OK button to close the Duct Plot Panel. The model should appear as in Figure 6 with alltime plots added.

Figure 6: Model with Time Plots Added

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Step 3 - Requesting Post-Processing Datasets

Show

SI Tutorial, Phase 2 - Running WAVE and

Creating Time Plots in WavePostStep 3 - Requesting Post-Processing DatasetsIn this step we will request that particular data that we may be interested in later be output forthe entire network, as opposed to certain locations as in the case of Time Plots. This is moreconvenient if the user wishes to have the data (e.g. Pressure, Temperature, etc.) at numerous pointsthroughout the network or is unsure, ahead of time, at which locations this data will be required forpost-processing. It also allows the user to do more advanced post-processing to be discussed later inthis tutorial.

3.1 Basic Datasets

Chapter sections

Example Input File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si1.wvm

3.2 Valve Datasets

Example Output File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si1.wps

3.1 Basic Datasets

Suppose we are not sure, beyond the behavior in the intake and exhaust ports, which behaviors wewill be interested in viewing results for at the end of the simulation. Later analysis might requireextensive amounts of data that we didn't request plots for ahead of time! It may also be inconvenientto return to WaveBuild and request more plots and rerun the model, especially if the model takes avery long time to run! We can avoid some of this by requesting Post-Processing Datasets inadvance.Open the Postprocessing Output Panel by selecting the Postprocessing Output... menu item fromthe Simulation pull-down menu. We have yet to request any data to be output after the simulation isrun through the WAVE solver, so the Requested Datasets list should be blank. By default, the Basicmodels are listed, which are datasets grouped together that are always available, no matter whichjunctions or physical models exist in the simulation. To request a specific dataset that we would likewritten to the simulation output file, highlight one by clicking on it and then click on the single arrowbutton pointing to the right to add it to the list of Requested Datasets (datasets can be multipleselected by holding down the Shift key to highlight a span of datasets or the Ctrl key to highlightmultiple, individual datasets). Clicking on the double-arrow button will move all datasets form a Modelgrouping in the the Requested Datasets list.

For this simulation, select the VELOCITY and VOLUMETRIC_FLOW datasets. When completed, thePostprocessing Output Panel should appear as in Figure 1.

Figure 1: Requesting Basic Datasets

3.2 Valve Datasets

At the top of the Postprocessing Output Panel, change the Models option menu to Valve. This willmake the Available Datasets list change to those contained in the Valve subset. All subsets besidesthe Basic subset are available depending upon the junctions or physical sub-models included in theanalysis.Highlightandadd DISCHARGE_COEFFICENT, FLOW_COEFFICIENT,and LIFT_OVER_DIAMETER to the Requested Datasets list. This will allow us to observe thedifference between the coefficient used and the one not-selected (CD vs. CF). When completed, thePostprocessing Output Panel should appear as in Figure 2.

Figure 2: Requesting Valve Datasets

Click on the OK button to save the changes and close the panel.

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Step 4 - Running WAVE and understanding the .out file

Show

SI Tutorial, Phase 2 - Running WAVE and

Creating Time Plots in WavePostStep 4 - Running WAVE and Understanding the .out FileIn this step we will run the model file through the WAVE solver and learn to parse the output file. Inthis and the following step, all output files created during the simulation will be examined and definedas to their purpose and use.

Chapter sections4.1 Running the Solver4.2 The .out File

4.1 Running the Solver

Example Input File:

The model has been run through an input check and is all set to create the requested data for postprocessing. To run the model through the actual WAVE solver there are two options: Run the model in screen mode by clicking on the Run Screen Mode buttonin the toolbar

Run the model in batch mode by clicking on the Run Batch Mode button

in the toolbar

Screen mode runs the model at high priority while sending standard output to the screen. A shell willopen and the simulation will pass by, printing output in real-time for the user to examine (output isalso printed to the .out file).Batch mode runs the model at reduced priority while sending standard output to the .out file. OnPC, a shell will open, noting the version of the solver being used, the window will minimize, and thesimulation will run "quietly" with no output to the screen. When the simulation is finished, the promptwill return in the opened shell. On UNIX, the process is detached from the current shell (similar toexecuting at the shell prompt with the "&") and run in the background. No indication of the process isgiven. Status of the simulation can be determined using the "ps -ef" command.If the model has been altered in any way and not yet saved (noted by the asterisk next to the filenamein the title bar), WaveBuild will prompt you to first save the file before running. Run the solver usingeither method and close the shell (if necessary) when the simulation is complete.

4.2 The .out File

Whilethesimulationisrunning,WAVEwillcreateatemporaryfilewiththe .hlt extension. The .hlt file will not be discussed here but this file will be automatically deletedupon successful completion of the simulation. If this file exists when the simulation completes, itusually indicates that the simulation failed while running in WAVE.To this point, we have been building the model and saving it along the way into a file witha .wvm extension. It is a simple XML format file that can be observed in any web browser bychanging the filename extension to .xml. There should now also exist .out, .sum, .wvd,and .wps files as well (a .rp file will have also been created for reverse compatibility with an olderpost-processor and will not be discussed it is obsoleted by the .wps file).The .out file, discussed and analyzed earlier after the input check, now contains additional dataabout the simulation. Open the .out file using any common text-editor and examine.First note the added requests for plots and datasets called out when the input file is parsed.BAS:TIMEI*** REQUESTED PLOT ID`S AND TITLES:PLOT #1 201 PressureLOCATIONS: DUCT: duct2PLOT #2 202 TemperatureLOCATIONS: DUCT: duct2PLOT #3 111 Linear P-V DiagramLOCATIONS: JUNC: cyl1PLOT #4 701 Engine TorqueBAS:DATASETS

DUCT: duct3DUCT: duct3

Next, note the output from the simulation during run-time.

Row (1) gives an abbreviation for what each column of data is displaying. This information may beuseful for debugging purposes in simulations that fail during run-time.

Row (2) is a summary for Cylinder #1 during engine cycle 0, the start-up cycle (WAVE simulations, bydefault, begin at IVC for cylinder #1 unless otherwise specified in the General Parameterspanel). Only Cylinder #1 will have results for engine cycle 0.Row (3) is a summary of engine system performance for engine cycle 0.Rows (4+) will be a summary of every individual cylinder in the system for each engine cycle followedby a engine system summary for each cycle.Starting at engine cycle 3, a line (8) denoting auto-convergence conditions is printed to theoutput. When auto-convergence conditions are satisfied (14), if the convergence detection wasactivated in the General Parameters panel, WAVE will run one more engine cycle and then finish thecase. This happens regardless of whether or not convergence conditions are satisfied in the followingengine cycle.The column titles as labeled in row (1) relate to the lines summarizing individual cylinderperformance. They are, in order Cylinder Number, Engine Cycle (cumulative from start of case),Timestep number (cumulative from start of case), Mass Airflow (kg/hr), Volumetric Efficiency, ExhaustPort Temperature [K], Equivalence Ratio, IMEP [bar], PMEP [bar], Indicated Horsepower [hp],Indicated Specific Fuel Consumption [g/kW*hr], Cylinder Pressure at IVC [bar], Cylinder Temperatureat IVC [K], and Trapped Fuel/Air Ratio at IVC.

Next, note the information on elapsed time, number of timesteps, and limiting elements in the system.The number of timesteps can be used to calculate the average timestep size in CA over the lastcycle (CA per cycle / #timesteps). Our engine is a 4-stroke engine so there are 720 in a singleengine cycle with 776 timesteps in the last engine cycle. This yields an average timestep size ofapproximately 0.93 close to the default maximum timestep size of 1 set in the GeneralParameters panel. Although there is no hard and fast rule, typical, well-built WAVE models won'thave a timestep below 0.1. If the timestep is smaller than this, it is usually due to poor modelingpractice (extremely small element size within the model).The limiting element information can be useful in finding an unreasonably small Discretization Lengthor Overall Length (for a duct) or Volume (for a y-junction) that may be slowing the simulation downdramatically. Note in this simulation that duct4 is the limiting element, with sub-volumes 1, 2, and 4showing up in the listELAPSED TIME OUTPUT:

TIME STEP OUTPUT:

CPU TIME (IN THIS CASE) =

WALL CLOCK TIME=

TOTAL STEPS IN LAST CYCLE = 776

0.28 sec.0sec.

LIMITING ELEMENT% STEPS (DOES NOT HAVE TO ADD TO 100)------------------------------------------------------------DUCT/VOL: duct4/169.1 DUCT/VOL: duct4/211.3

DUCT/VOL: duct4/4

18.4

Finally, general result information is printed in tabular format, printable for records or reports. Resultsincluded are Final Output of all elements in the system (ducts and junctions); EngineSummary; Breathing Quantities; Fuel Burn Progress Summary, Engine Geometry, OperatingConditions, Predicted Performance, and Engine Out Emissions; and Valve and Emissions specificoutput. The output contained from this point forward varies for what is included in the model(turbine/compressor, emissions modeling, etc.). Examine this portion regularly to grow more familiarwith WAVE output for different models!

Proceed to Step 5 - Introduction to Post-Processing and WavePost

Show

SI Tutorial, Phase 2 - Running WAVE and

Creating Time Plots in WavePostStep 5 - Introduction to Post-Processing and WavePostIn this step we will examine the files created by WAVE for post-processing and use WavePost toexamine and create Time Plots from the simulation. We will also observe how WavePost displaysCycle Average quantities using datasets requested in WaveBuild.

Chapter sections5.1 The .sum File5.2 The .wvd File5.3 The .wps File5.4 Time Plots in WavePost5.5 Cycle Average Results

Example Input File:

5.1 The .sum File

At the end of the simulation, WAVE should have created a .sum file. The .sum file is a simple ASCIItext file that can be viewed using any text editor, but is intended for use by the WavePost postprocessor.The .sum file contains a group of name=value pairs that detail the cycle-averaged results for eachcase in the simulation. Cycle-averaged results are single-number values detailing results that arecalculated as an average over the entire last cycle in the simulation. Examples include Torque,Power, and Fuel-Consumption (a list of what each name in the .sum file equates to can be found inthe WAVE Help). At the end of the output for each case, all constants, including pre-definedconstants, are also listed with the values used.Open the .sum file and examine:SUM:

5.2 The .wvd File

WAVE also will create a .wvd file. The .wvd file is a binary file (not legible in a text-editor) written inRicardo SDF (Standard Data File) format and is also intended for use by the WavePost postprocessor. Data for requested time plots and datasets are stored in the .wvd file. If necessary, thisdata can be extracted by using either the SDFBrowser or the sdftoascii command-line program, bothinstalled with WAVE. The .wvd file also stores a copy of the network layout and other keyinformation for post-processing. This file is vital to running the WavePost post-processor and shouldnot be tampered with by editing, renaming, etc.

5.3 The .wps File

When any time plots are requested in WaveBuild, WAVE will create a .wps file at the end of theanalysis. The .wps file is also an XML format file that can be observed in any web browser bychanging the filename extension to.xml. It is simply a session file (template) for the WavePost postprocessor detailing what information to extract from the .wvd file for requested time plots that arecreated during the WAVE simulation.When WavePost is launched directly from WaveBuild, it will look in the working directory fora .wps file with the same prefix as the currently loaded .wvm file in WaveBuild. If it exists, the file isopened in WavePost and the .wvdand .sum files from the same simulation are assumed to be theresults set for analysis.

5.4 Time Plots in WavePost

Launch WavePost from WaveBuild by clicking on the WavePost button in the toolbar. TheWavePost GUI will open and automatically load the .wps created by WAVE (since we requested timeplots in WaveBuild). The network should appear in the main WavePost window identical to itsappearance in WaveBuild (see Figure 1).

Figure 1: WavePost GUI

The Results Frame in the lower right corner of WavePost shows all results available in the currentsession file. Plots are categorized as Time Plots, Sweep Plots, Spatial Plots, or TCMAPPlots. The Time Plots that we requested in WaveBuild have been automatically created and arelisted in the tree under the Time Plots folder. Double-click on the Pressure plot to see the result(see Figure 2). Notice that this plot has a data line for the single element in duct2 as well as both ofthe elements in duct3, where we decided to "Use All Locations".

Figure 2: Time Plot of Pressure in duct2 and duct3

Each plot can be individually opened and edited. Elements of the plot, such as the data line, theaxes, the title, etc. are all selectable and changeable. Individual data curves can be hidden throughthe Curve Selector Panel (Tools > Curve Selector...). Data can also be Cut, Copied, and Pastedbetween plots. A single plot can also be Cloned (File > Clone) to create an exact copy of a plot touse as a template for new data.Data can be added to a plot from the existing results (Add > Data...) or imported from an ASCII textfile, Ricardo SDF-formatted file, or, on PC, from an MS-Excel file (File > Import > Excel...,ASCII..., or SDF...). Data on an existing plot can also be exported to an Excel file (on PC) or to anASCII text file by selecting the File > Export... pull-down menu item.Plots can be printed directly to a printer or to an image file by clicking on the Print buttontoolbar.

in the

The plots that were pre-requested in WaveBuild are already created and listed under the TimePlots folder. But we also requested some Basic and Valve Datasets. This data has been stored inthe .wvd file and we can now create our own time plots using this data. We will create an overlay ofValve Flow Coefficient (CF) and Valve Discharge Coefficient (CD) vs. non-dimensionalized valve lift(L/D).Right-click on the Time Plots folder and select the Add Time Plot... option a blank time plotwindow will open. Select the Data... option from the Add pull-down menu to open the Time DataPanel. In the Output Sets option menu, highlight the single set that is available(named filename.wvd:Case 1). In the Independent Variable (X) section of the panel, selectthe Custom option and then click on the Edit... button to open the X Axis Selector Panel. Highlightthe Junction Cyl1 Intake 1 option in the Elements option menu and select Valve Lift Over

Diameter in the Variables option menu. The X Axis Selector Panel should appear as in Figure 3,below.

Figure 3: X Axis Selector Panel

Click the OK button to save the selections and close the panel. Back in the Time Data Panel, underthe Elements option menu, highlight the Junction Cyl1 Intake 1 option and pick Valve FlowCoefficient in the Variables option menu. When finished, the Time Data Panel should appear asin Figure 4.

Figure 4: Time Data Panel

Click the OK button to save the settings and close the panel. The data curve for Flow Coefficient willappear in the Time Plot and the plot title and axis labels will be automatically generated. Double-clickon the plot title and edit it to read "CF and CD". Double-click on the Y-axis and edit the label to read"Valve Coefficient" (delete the word Flow). Double-click on the X-axis and edit the label to read"L/D". Double-click on the plot frame (easiest to do at the top or right-edge of the plot) and click inthe Grid checkbox.Highlight the data curve and, using the Copyand Pastetoolbar buttons, paste a second datacurve on the same plot. Double-click on the second data curve in the legend to open the CurvePanel. Click on the Edit Databutton and then click on the Modify Data Source button. Change theVariable to VALVE:DISCHARGE_COEFFICIENT and click on the OK button to save thechange. Don't forget to update the Legend in the Curve Panel to reflect the change from flow todischarge coefficient. Finally, in the "Plot" pull-down menu, change the option from "Cyclic" to"XY". When finished, the Time Plot should appear as in Figure 5. Close the Time Plot and note thata fifth plot is in the list under the Time Plots folder named "CF and CD".

Figure 5: CF and CD Plot for cyl1 Intake Valve

Time plots can also be made quickly by right-clicking on an element in the flow network diagram andselecting a variable to plot. Right-click on duct1 to create a time plot of Velocity atlocation 0.0 (Figure 6) and right-click oncyl1 to create a time plot of Pressure (Figure 7).

Figure 6: Velocity Time Plot at duct1, Location 0.0

Figure 7: Cylinder Pressure Time Plot at cyl1

5.5 Cycle Average Results in WavePost

Any dataset that stores data for elements (cells/junctions) which was requested in WaveBuild can bedisplayed as color contours on the flow network diagram. In the Results Frame in the lower rightcorner of WavePost, right-click on the Average folder under the Network Displays folder. This willopen the Average Panel and will automatically redraw the model canvas to display the flow networkas a simple scaled model; the ducts and junctions are redrawn with relative diameters displayed andcolor contours to represent the selected variable. Change the name to Case #1 Velocity and selectthe Velocity variable, then click the OK button to close the panel. This creates the Network Displayin the Average folder named Case #1 Velocity.The scale at the bottom of the window automatically sets upper and lower bounds by using thehighest and lowest calculated values from the dataset. These can be controlled in the Contour MapPanel (accessible from the Average Panel, or by double-clicking on the contour bar at the bottom ofthe canvas) using the slider bars or by typing numerical values in the given text fields.

Figure 8: Cycle Average Velocity

Save your file

Save this WavePost session file (.wps) by selecting the Save As... option from the File pull-downmenu. It is important to save a WavePost file under a different name when it has been edited (plotscreated, changed, etc.) since WAVE will overwrite the file every time the solver is run. If you wouldlike to rerun the model file and still have access to the plots and network displays you've just createdsave the .wps file to the same directory with a new name.

With these five steps, we will create a parameterized 4-cylinder model that runs un-throttled over arange of 1000-6000 rpm. We will then observe the behavior of the engine over the speed range bycreating Sweep Plots in WavePost.

WavePostStep 1 - Copying and Pasting the Single-Cylinder ModelTime and effort can be saved when creating our 4-cylinder model by using the existing single-cylindermodel as a template. Copy and Paste functionality can be used to create three copies of the singlecylinder network, including the attached ducts representing the ports. The engine information thenneeds to be updated to reflect the addition of three new cylinders.

1.1 Detaching the Ambient

1.1 Detaching the Ambient Junctions

Thesingle-cylindermodelcurrentlyhasAmbientjunctionsatbothends,named Intake and Exhaust. We don't need to include these when replicating the enginenetwork. These ambient junctions can be detached and moved aside for the time being.Middle-click on the end of duct1 that is attached to the Intake ambient. Holding the middle-mousebutton down, drag the end of duct1 out onto the canvas and release the mouse button. This willdetach the duct from the ambient. Repeat for the end of duct4 attached to the Exhaust ambient.Using the middle mouse button, drag the Intake ambient further to the left, to move it out of theway. Repeat for the Exhaust ambient, moving it further to the right. When finished, the model shouldappear as in Figure 1.

Figure 1: Ambients Detached from Ducts

1.2 Copying and Pasting the Network

The engine-cylinder network, with the attached ducts representing the intake and exhaust ports, isidentical for all four cylinders in the engine. We can therefore copy and paste the existing singlecylinder network three times to create the other cylinders in our 4-cylinder engine. Using the leftmouse button, draw a box around the ducts and engine-cylinder network to select the entire system(be careful not to draw the box around the ambient junctions). All of the selected items within the boxwill be highlighted in red. Click on the Copy button in the toolbar . Then click on the Pastebuttonin the toolbar and the mouse pointer will become a crosshair icon. Click on the canvasbeneath the cyl1 junction and a duplicate network will be created. Click on the Paste buttonandplace the duplicate network two more times to create four identical duct/junction networks torepresent all four engine-cylinders. Note that the ducts and junctions have all been numberedsequentially.Plot requests are not duplicated, thus no plots are dangling off of any of the newly createdducts/cylinders (feel free to request new plots if desired). To hide the plots that currently exist on thenetwork, right-click anywhere in the white canvas area and select the Edit CanvasProperties... option from the menu to open the Canvas Properties panel. De-select the Plots togglebutton in the Annotations section of the panel (see Figure 2).

Figure 2: Canvas Properties panel

This will simply hide the plot icons and not draw them on the canvas. When finished, the modelshould appear as in Figure 3.

Figure 3: Single Cylinder Flow Network Duplicated

1.3 Creating an Engine Block Icon

Adding an Engine Block icon to the canvas will provide a clickable and selectable object, enablingdirect access to the Engine General Panel (previously accessed through the Model pull-down menuor an engine cylinder junction) and also allow for right-click selection to add plots and otherattachments (sensors and actuators to be discussed in later tutorials).Select the Create Engine... option from the Tools pull-down menu to open the Create EnginePanel. This panel displays currently entered geometric values from the Engine GeneralPanel. Currently, there is only one cylinder in the engine -- this must be updated to reflect that threenew cylinders have been added. Change the No. of Cylinders text field to 4 and pressthe Enter key. This will update the Preview of the engine block on the right as well as the FiringOrder table at the bottom. The Firing Order table will automatically calculate the TDC (top deadcenter time) for each cylinder based upon the No. of Cylinders value and the Strokes perCycle selection (TDCs are calculated for even firing intervals and are relative to the previous cylinder,with the first firing cylinder at crank-angle 0). Change the Firing Order to reflect that of a standard 4cylinder engine 1, 3, 4, 2. The default spacing of the cylinder TDCs will be appropriate for thistutorial. When completed, the Create Engine Panel should appear as in Figure 4.

Figure 4: Create Engine Panel

Click the OK button to close the panel and note the Engine Block icon that is added to the canvas.When the Engine Block is created, it will have four Engine Cylinder junctions created along with itby default. Left-click each of these newly-created Engine Cylinders one at a time (they will highlightin red) and press the Delkey to delete them, leaving an empty Engine Block icon. Move the EngineBlock icon over to the Engine Cylinders that are currently on the canvas by middle-clicking on theicon and dragging it. The existing Engine Cylinderjunctions can be "dropped" into the icon bymiddle-clicking on them, one at a time, and placing them over the cylinder place-holders on theicon. They will snap into place on the icon and be associated with the icon from that point on. Thebore-spacing of the Engine Block icon can be adjusted by right-clicking on the icon andselecting Appearance... from the menu. Default WaveBuild grid spacing is 40/square so, if thecylinder junctions are placed 3 grid squares apart, use a spacing of 120 (see Figure 5).

Figure 5: Engine Block Icon Appearance

When completed, the model should appear as in Figure 6.

Figure 6: Model with Engine Block Icon

Save your model

Select the Save As... option from the File pull-down menu and give the model a new name, suchas tut_si4.wvm.

Proceed to Step 2 - Joining the Cylinders using a Simple Y-Junction

WavePostStep 2 - Joining the Cylinders Using a Simple Y-JunctionA simple Y-junction will be used to join all four engine-cylinders together at the intake ports. This willrepresent a large spherical plenum with a single intake pipe that will connect to the existing Intakeambient junction. The same will be modeled on the exhaust side.

Example Input File:

Junctions on the Canvas2.2 Defining the Simple YExample Output File:Junctions.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4.wps

2.1 Placing the Simple Y-Junctions on the Canvas

Y-junctions are used anywhere a volume needs to be modeled that has more than one connectionpoint. They are also used to represent arbitrarily-shaped volumes with an aspect ratio inappropriatefor modeling by a duct. This includes T-Junctions, Exhaust Collectors, Catalytic Converter cones, AirFilters, etc. The Y-junction is represented by a volume and surface area and can have as many ductsconnected as desired, but must have at least oneconnection.There are two different Y-Junctions: Simple and Complex. The Simple Y-junction is assumed to bespherical in shape and requires minimal input a diameter defines the volume, surface area, andcharacteristic flow values required for the junction. Complex Y-junctions are more flexible but alsorequire more user-input. They are used to define any arbitrary shape desired. For this section of thetutorial, we will use Simple Y-junctions to connect the intake and exhaust cylinders into one inletsource and one exhaust sink.Drag and drop one Simple Y-junction on each side of the engine near the middle, vertically(see Figure 1).

Figure 1: Simple Y-Junctions on the Canvas

Connect the dangling duct ends to the Simple Y-junction by dragging and dropping (use themiddle-mouse button) anywhere on the blue portion of the junction. Any duct end dropped onto theblue portion of the junction will create its own connection point automatically. Dropping the danglingduct end on the existing connection point, , will occupy that connection point, leaving no startingpoint to draw a duct away from the Y-junction. If there are no connection points on a Yjunction and a duct must start at that junction and be drawn away from it (to follow the Left to Rightconvention), simply left-click on the blue portion and drag a duct away from the Y-junction.Create a new duct between the Intake ambient and the Simple Y-junction on the intakeside.Enter 50 [mm]forboth Left and RightDiameters and 500 [mm]for OverallLength. The Discretization Length should be 35 [mm], as used earlier in the single-cylindermodel. The default initial conditions are suitable for this duct.Create another new duct between the Simple Y-junction on the exhaust side andthe Exhaust ambient (following the Left to Right convention). Enter 50 [mm] for both Left and RightDiameters and 500 [mm]for OverallLength.Enter 40 [mm]forthe DiscretizationLength.Appropriateinitialconditionsforthisductshouldbesetas 1.05 [bar] Pressure, 700 [K] Temperature, and 650 [K] Wall Temperature. When completed, themodel should appear as in Figure 2.

Figure 2: All Ducts Connected

2.2 Defining the Simple Y-Junctions

The Simple Y-junctions must be fully defined before the model will run. We must define thegeometry of the junction as well as the orientation for all of the connected ducts.Double-click on the intake-side Y-junction to open the Simple Y-Junction Panel. The geometry forthe Y-junction is defined using only a Diameter value, as the junction is assumed to be spherical inshape. The volume and surface area are therefore easily determinable using the entered Diametervalue. Type 50 [mm] in the Diameter text-field. The default coefficients and initial conditions aresuitable for this tutorial (see Figure 3).

Figure 3: Intake-side Simple Y-Junction Panel

Click on the Edit Openings button to orient the connected ducts.

A new window will open with a graphical representation of the junction and the connected ducts. Thegreen sphere represents the volume occupied by the Y-junction, while the connected ducts are scaledin size, relative to the size of the green sphere, based on the duct diameters. The currently-selectedduct is colored solid red in the window while the other ducts are drawn in translucent gray. Thejunction/ducts can be rotated in 3-D space by holding the Shift button while clicking and dragging inthe window using the middle mouse button.For each attached duct, the orientation needs to be given using three angles to describe the ductposition relative to the X, Y, and Z axis. If the entered values for these angles do not sum correctly(i.e. the defined angles are geometrically impossible to orient the duct in 3-D space), all three fieldswill turn red to indicate the error. Once corrected, the fields will turn green again.You can define the directions of positive and negative rotation and there is no right or wrongway. Once a convention for the X, Y, and Z rotations has been established for a junction, this shouldbe adhered to for all the ducts joined to this junction. If possible, it is often easier to keep one planeflat when dealing with a junction, thus reducing the number of angles that need to be computed.For the sake of this tutorial, assume that rotation in the clockwise direction is positive. Although theorientation of each duct is only important relative to the other ducts at the junction, it is usually easiestto orient the ducts similarly to the appearance on the canvas (if the orientation on the canvas is closeto the true orientation). Orient the ducts leading to cylinders 1 and 4 at 60 degrees off the xaxis and the ducts leading to cylinders 2 and 3 at 30degrees off the x-axis. They should beoriented similarly to how they appear on the WaveBuild canvas in Figure 2. When completed, theOpenings panel should appear as in Figure 4.

Figure 4: Openings Panel for Simple Y-Junction 1

The exhaust-side Simple Y-junction should be set up similarly, with a Diameter of 50 [mm] andinitial conditions similar to the outlet duct Pressure of 1.05 [bar], Temperature of 700 [K], and WallTemperature of 650 [K]. The orientation of the ducts should be similar to that of the layout on thecanvas, as in the intake-side Y-junction. When completed, the Simple Y-junction Panel and Openingspanel should appear as in Figure 5 and Figure 6below, respectively.

Figure 5: Exhaust-side Simple Y-Junction Panel

Figure 6: Openings Panel for Simple Y-Junction 2

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Step 3 - Creating a Multi-Case Speed Sweep

Step 3 - Creating a Multi-Case Speed Sweep

The model is complete. To get useful results from this model, you need to set up the runconditions. A popular application is to have multi-case runs that cover the engine RPM range ofoperation. From such runs, one can calibrate or study the Torque (Power, Volumetric Efficiency, etc.)curves of the engine over the range of operation. In this section you will learn how to incorporatemulti-case runs into the WAVE engine model.

Example Input File:

3.1 Adding Cases with the

3.1 Adding Cases with the Case Manager

Cases can be added and deleted using the Case Manager at the bottom of the WaveBuildcanvas. Click on the Add Case button 5 times to create 5 more cases for a total of 6 cases.WARNING: It is dangerous to edit the model in any case other than Case #1 as changing theelements, components, or general behavior between cases can cause WAVE to crash at runtime. Therefore when in any case other than Case #1, the background of the case text field willbe red to warn the user as in Figure 1.

Figure 1: Case Manager when case other than Case #1 is selected

Make sure to return to Case #1 before continuing by either typing directly into the text field or usingthe arrow selection buttons.

3.2 Changing Constants between Cases

The convenience of using multiple cases is that Constant values can be changed from case to case.For this tutorial, we will step from 6000 rpm down to 1000 rpm, using 1000 rpm increments tosimulate multiple steady-state test points in a speed sweep. Open the Constants Paneland notethat there are now columns added to the table for every new case created. Also note that the valuesfrom Case #1 are filled in for all of the new cases, using light-gray text. The light-gray text denotesthat the value is carried over from the previous case. If no new value is provided for a constant,WAVE assumes that the value used in the previous case is suitable.Select the Case #2 field for the SPEED constant and enter 5000. Enter 4000 - 1000 for Cases #3 #6, respectively. The Constants Panel should appear as in Figure 2. Click OK to close the paneland save the settings.

Figure 2: SPEED values in Constants Panel

When running a speed-sweep simulation, it is recommended to start at the high speed and movedownwards toward the low speed. This is because the WAVE solver is actually working in a timebaseof seconds and the solution tends to converge based on the number of repeated engine cycles. Morecycles can be completed at high RPM in a given amount of time in seconds than at low RPM. Thismeans a system running a high RPM will tend to finish quicker than at low RPM, thus any problemswith the general setup may be detected earlier when starting at a high RPM.Typically, with a change in engine speed other parameters change as well, such as combustionbehavior and cylinder temperatures.Double-click on the Engine Block icon to open the Engine General Panel. Click onthe Heat Transfer tab and enter {PISTON_TEMP}, {HEAD_TEMP}, {LINER_TEMP}, {IV_TEMP},and {EV_TEMP} in the text fields for the Piston Top, Cylinder Head, Cylinder Liner, Intake Valve,and Exhaust Valve temperatures, respectively. Click on the Apply button and a message willappear as show in Figure 3.

Figure 3: Undefined Constants Message Box

WaveBuild has detected that new constants have been used but are not defined in the ConstantsPanel. Click on the Yes button to open the Edit Constants panel and edit the profiles for these fivenew constants. Enter the values as shown in Figure 4 These profiles describe the temperature ofthe combustion chamber cooling slightly with a decrease in engine speed. Click OK to save theseconstant profiles and close the Edit Constants panel.

Figure 4: Profiles for Combustion Chamber Temperatures

Click on the Combustion tab and enter {CA50} in the Location of 50% Burn Point text fieldand {BDUR} in the Combustion Duration (10-90%) text field. Click on the Apply button again to bequeried on adding these constants to the table. Select Yes from the Query window and enter theprofiles as given in Figure 5. These constants help to describe the shorter crank angle duration ofcombustion and retarding of spark timing at lower engine speeds. Click OK to save these constantprofiles and close the Edit Constant panel.Click the OK button to close the Engine General Panel.

Figure 5: Profiles for SI Wiebe Function Inputs

Save your model

Click on the Save button in the toolbarto save the file and then click on the Run Screen Modebuttonto launch the analysis (note how engine cycles take longer to complete in the later cases, atlower engine speeds).

Proceed to Step 4 - Changes in the .out and .sum Files

WavePostStep 4 - Changes in the .out and .sum FilesWith a multi-case, 4-cylinder model, there are some changes in the .sum and .out files of note. Wewill open both files and observe what is different from the single-cylinder output.

Chapter sections4.1 Changes in the .out File

Example Input File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4.wvm

4.2 Changes in the .sum File Example Output File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4.wps

4.1 Changes in the .out File

Using your favorite text-editor, open the .out file created by the run. First, note that the simulationinitializes by running an engine-cycle 0 only for cylinder 1. Then, for every engine-cycle following,data for each cylinder in the 4-cylinder engine is printed:

Also note that the same output created for the single-cylinder, run is created for each case in themulti-case run.At the beginning of the output for Case #2, note the warning statement:W*** FLOW FIELD NOT REINITIALIZED AT START OF THIS CASE

This warning tells us that the initial conditions for Case #2 are set by using the final conditionsfrom Case #1 (controlled by the Reinitialize Flowfield Between Cases toggle button on the GeneralParameters Panel). Note that there is no engine cycle 0 for cylinder 1 in any of the casesfollowing Case #1 since no re-initialization occurs. This practice usually saves the simulation a fewengine-cycles in each case as it is initialized using conditions that are most-likely closer to theconverged results than those specified by the user when setting up the simulation. For the six cases

in this simulation, the reduction in the number of cycles is noted in the table below, showing that atotal of 10 (35 - 25 = 10) fewer engine-cycles are performed if reinitialization is skipped in thismanner:NUMBER OF CYCLES REQUIREDCase #

ReinitializedFlowfield

Non-reinitializedFlowfield

Total

35

25

4.2 Changes in the .sum File

Open the .sum file with a text-editor and note that there is a set of cycle-averaged summary outputsfor every case in the simulation. The end of a case results set is delimited by a # sign, while the startof a new case results set is delimited by a CASE: line and followed by a TITLE line as below (notethat the {SPEED} constant in the title is updated for every case):

Proceed to Step 5 - Creating Sweep Plots in WavePost

WavePostStep 5 - Creating Sweep Plots in WavePostThe output files created by WAVE for use in WavePost (the .sum and .wvd files) now containinformation about the simulation for all six cases in the model. Sweep Plots can be created inWavePost to illustrate change in output values over the speed range of the model.

Chapter sections5.1 Multi-case Handling in

Example Input File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4.wvm

WavePost5.2 Creating Sweep Plots

Example Output File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4.wps

5.1 Multi-case Handling in WavePost

Launch WavePost from WaveBuild by left-clicking in the Launch WavePost button in the WaveBuildtoolbar .By default, WavePost opens a .wps file with the Time Plots folder opened in the Plots folder tree(see Figure 1). All plots that have been created by default, from plot requests in WaveBuild, arenamed by the plot type. Hence similar plots from different cases have the exact same name. Thiscan be confusing when trying to select the plot from a specific case.

Figure 1: WavePost Plot Tree

There are two ways to distinguish which plot is from which case:1. The plots are listed in order of case, from Case #1 upwards. In a run with a small number ofcases, it's easy to pick out the correct plot.2. If there are too many plots listed to make this practical, then the plots can be filtered by casenumber. Check the Show selected case box above the Plots folder tree, this will enable thefiltering by case number. Then, expand the results file list in the Results File folder tree andselect the desired case by left-clicking on the case icon. This will filter the plots and onlydisplay those with data from the selected case (see Figure 2).Selecting a case in this way will also change the behavior of displayed results. Manually-createdTime Plots and cycle-averaged results or animations (discussed in Phase 4) will display results fromthe selected case.

Figure 2: Filtering Plots by Case

5.2 Creating Sweep Plots

Sweep Plots are plots of cycle-averaged results from all cases in the analysis, using output found inthe .sum file. Using the results from our multi-case analysis, which simulates the engine over therange of operating speeds from 6000 down to 1000 rpm, we can create plots of any output parameterfound in the .sum file (e.g. torque, power, etc.) vs. engine speed or against any other desiredparameter.To create a sweep plot, right-click on the Sweep Plots folder in the Plots Frame and selectthe Add Sweep Plot -> 2D Plot... menu items (see Figure 3).

Figure 3: Creating a New Sweep Plot

This will create a new Sweep Plot named Sweep Plot #1 by default. The plot is empty, with no datadisplayed. To add data, select the Add pull-down menu and then select the Data... menu item toopen the Sweep Data Panel. This contains a list of all of the keywords in the .sum file that correspondwith a cycle-averaged numeric value. The list defining .sum file keywords and their associatedunits is available in the WAVE Help section. Selectbhp for the Dependant Variable (Y) andselect rpm for the Independent Variable (X). The Sweep Data Panel should appear as in Figure4 when completed. Click the OK button to apply.

Figure 4: Sweep Data Panel

WavePost will automatically label the axes (with units) by the .sum variables selected and namethe curve by the filename and keyword selected. Double-click on the axes or the curve to edit thesenames. Double-click on the title and edit the name to Power vs. Engine Speed. A different (butcompatible by conversion) units system can be selected for the axis so that users can choose howdata is displayed without doing clumsy numerical conversions manually. When completed, the plotshould appear similar to Figure 5.

Figure 5: Power vs. Engine Speed

WavePost can also easily create Default Sweep Plots, where a summary quantity from an element inthe model can be plotted against a default X-Axis. The default X-Axis used can easily be set byexpanding the Defaults sub-folder under the Sweep Plots folder the first branch of the expandedtree is the X-Axis Settings. Double-clicking on this branch will open the Default Sweep Plot X-AxisPanel, as shown below in Figure 6.

Figure 6: Default Sweep Plot Setting

If an engine exists in the model, "RPM" will be selected by default. Alternatively, you can select"Case" or "Cycle" ("Time" is allowed in a non-cyclic run). Otherwise, you can also select any othersummary quantity by selecting the "Custom" option. Click the "OK" button to close the panel.Right click on the engine block icon and create a sweep plot of torque (Add Sweep Plot >Performance > Brake Torque vs. > RPM). The sweep plot will open and be added to the plots inthe results tree. Use this method to create a plot of volumetric efficiency as well. The completedplots should appear as in Figures 7 and 8.

Figure 7: Torque vs. Engine Speed

Figure 8: Volumetric Efficiency vs. Engine Speed

Save your file

Click on the File pull-down menu and select the Save As... option to save the .wps session file undera new name, such as Comparison.wps, so that it won't be overwritten by WAVE in the event thatthe model file,tut_si4.wvm, is re-run.

Proceed to Phase 4 - Adding the Intake System and Creating Animations in

WavePost

Show

SI Tutorial, Phase 4 - Adding the Intake

System and Creating Animations inWavePostThe Intake or Induction system consists of a snorkel, air cleaner with filter, zip tube, throttle body, andintake manifold. All of these parts will be modeled in WaveBuild to create the induction system withappropriate restrictions.

Phase 4 Steps

Optional Starting Point:

1 The Snorkel and

Zip Tube2 The Air Cleanerwith Filter3 The ThrottleBody4 The IntakeManifold5 CreatingAnimations inWavePost

With these five steps, our model will have a complete air induction system that is representative of areal engine. Each part of the system will be discussed and modeling practices examined. Animationswill be created in WavePost for reporting and data analysis.

Show

SI Tutorial, Phase 4 - Adding the Intake

System and Creating Animations inWavePostStep 1 - The Snorkel and Zip TubeThe intake sub-system, leading up to the intake manifold, consists of a snorkel, air cleaner, zip tube,and throttle body. The snorkel and zip tube can be easily modeled with just ducts and orificejunctions, so it is easiest to draw them on the canvas first. We will skip over the air cleaner in thisstep and return to model it in step 2.

Chapter sections Example Input File:

Example Output File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4_intake.wps

1.1 Detaching the Intake Ambient Junction

Before performing any actions make sure the model is in Case #1.The 4-cylinder model as created has all four intake ports joined together at a single Simple Yjunction. The intake ambient junction will be re-used upstream of the induction system as theatmospheric conditions before the snorkel, but the Y-junction and duct created for the 4-cylindermodel can be selected and deleted. Highlight both the intake-side Simple Y-junction andupstream duct (holding down the shift key and left-clicking) and hit the Delete key. This will leave allfour intake port ducts dangling with no junction to attach to upstream (see Figure 1). These willeventually be attached to the ends of the runners from the intake manifold. For now, they can remainunattached.

Figure 1: Y-Junction and Upstream Duct Deleted

Click and hold the middle mouse button to move the ambient junction named Intake down to thebottom of the canvas. This will serve as the starting point for the induction system.

1.2 Placing the Required Orifice Junctions and Ducts

The snorkel and zip tube can easily be modeled using only orifice junctions and ducts. A schematicof the system with required dimensions is shown in Figure 2.

Figure 2: Snorkel and Zip Tube Schematic

Place orifice junctions and connect with ducts as shown in Figure 3. In place of the air cleaner,place two Complex Y-junctions and connect with a duct. Remember to follow the Left to Rightconvention when creating the ducts.

Figure 3: Flow Network

To make the last duct in the zip tube (duct22 in Figure 3) appear bent on the screen, right-click onthe duct and select Add Control Point from the menu:

A control point can be selected with the middle mouse button and moved to make the duct appearbent (it will snap to grid points just like junctions do). Multiple control points can be added to aduct. Using two control points diagonal from each other by one grid square will create theappearance of a smooth 90 bend, as shown in Figure 4.

Figure 4: Control Points to Draw Bent Duct

1.3 Defining the Ducts (Tapered and Bent)

Using the schematic from Figure 2, above, edit the ducts representing the snorkel and zip tube andenter the appropriate Diameters and Lengths (leave the Complex Y-junctions and duct betweenthem for later). Remember to use 35 [mm] for the Discretization Length for all ducts in the intakesystem and set initial conditions to be 1 [bar] Pressure, and 300 [K] for Initial Fluid and WallTemperatures.Note that when setting the Left Diameter of the first duct to 70 [mm] and the RightDiameter to 50 [mm], with Overall Length of 50 [mm], the Taper Angle field turns yellow, indicatinga warning that the calculated taper angle of11.3099 is outside of the recommended range for thisparameter (see Figure 5). Read this sidebar on modeling tapered ducts and note that we aremodeling upstream of the intake manifold, thus expect constant flow into the engine. Flow will alwaysbe contracting and therefore the slightly high taper angle is not of concern.

Figure 5: High Taper Angle

Also note that when entering dimensions for the last duct in the zip tube, the 90 Bend Angle shouldbe included (see Figure 6). The Bend Angle field on the Dimensions tab of the Duct Panel allowsthe user to specify how much of a bend occurs across the entire length of the duct. The pressuredrop due to this bend is also then distributed across the entire length of the duct.

Internally, the WAVE solver uses this Bend Angle, the average Diameter of the duct, and the ductOverall Length to calculate a Cp value based on simple equations (see the WAVE Help section onducts for more details). If you would like to specify your own Cp value, simply set the Bend Angle to0 and set the Pressure Loss coefficient on the Coefficients tab. The Cp value is then divided evenlyamongst the number of elements in the duct and then the pressure loss in each element is calculatedby:

When completed, the intake subsystem should appear as in Figure 7.

NOTE: The Cp values calculated by the bend angle and entered in the Coefficients tab will beadded together if they are both specified!

Figure 7: Intake Subsystem

Save your model

Select the Save As... option from the File pull-down menu and give the model a new name, suchas tut_si4_intake.wvm. Saving this file and running it with a different name will allow comparisonof results to the models built and analyzed earlier.

Proceed to Step 2 - The Air Cleaner with Filter

Show

SI Tutorial, Phase 4 - Adding the Intake

System and Creating Animations inWavePostStep 2 - The Air Cleaner with FilterIn the last step, two Complex Y-junctions were placed on the canvas with a duct connecting them torepresent the air cleaner and filter. In this step, we will define these junctions and duct toappropriately represent the physics of the system in WAVE.

NOTE: This modeling method is only appropriate for performance simulations. Acousticsimulations should model the air cleaner volumes in smaller sub-sections and the filter withnumerous perforates!

Chapter sections Example Input File:

Example Output File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4_intake.wps

2.1 Defining the Complex Y-Junctions

A schematic of the air cleaner geometry is shown in Figure 1. It is simply two cylindrical volumesseparated by a flat, circular filter. It is impossible to appropriately model the filter passages true to lifeas flow through a fibrous filter is very non-one-dimensional. Typically, a filter is modeled as an orificethat approximates the pressure drop of the real system.

Figure 1: Airbox Schematic

For our model, the two Complex Y-junctions will represent the two cylindrical volumes and the ductconnecting them will represent the filter. Double-click on yjun1 and enter the appropriate values asgiven in Figure 2.

Figure 2: Airbox Network Representation

Notetheauto-calculatorbuttonsprovidedforboth Volume and HeatTransfer/Skin Friction Area fields. Clicking on either of these will assume a spherical shapeandcalculate Volume or Heat Transfer/SkinFrictionArea accordinglyfromthe Diameter value (this is identical to using a Simple Y-junction -- allowing the user to entertheir own value is what makes the Complex Y-junction flexible)!

Click on the Edit Openings button to orient the connected ducts.

DuctsareorientedsimilarlyasontheSimpleY-junction.Theorientationof duct19 and duct20 should be used as shown in Figure 1. Note the new fields for each connectedduct: DELX, DIAB, and Thick.DELX, sometimes referred to as the characteristic length, is the distance from the duct connectionpoint across the volume. See Figure 3 for a diagram of the DELX values for both Complex Yjunctions.

Figure 3: DELX Values

DIAB, sometimes referred to as the expansion diameter, is the equivalent diameter for the maximumarea that the gas can expand into, perpendicular to the duct entrance. See Figures 4 and 5 fordiagrams for the DIAB values for both Complex Y-junctions.

Figure 4: DIAB Values for duct20 and duct21

Figure 5: DIAB Value for duct19

Thick is the orifice thickness and is used in acoustics simulations to calculate the acoustic endcorrection. It is not necessary to set this value in performance simulations as it has no effectwhatsoever on the outcome.When completed, the orientations for the Complex Y-junctions should appear as shown in Figures6 and 7.

Figure 6: Orientation Panel for 1st Complex Y-Junction

Figure 7: Orientation Panel for 2nd Complex Y-Junction

2.2 Representing the Filter as a Massless Duct

The filter will be modeled as a massless duct (overall length of 0) and will act like an orifice platebetween the two volumes by having a smaller diameter than the surrounding volumes.Typical information provided for an air filter is a pressure drop achieved at a given mass flow rate(most frequently, near the maximum expected mass flow rate). For our air filter, we are supplied withthe information the filter creates a 1.25 kPa pressure drop across the system at a flow rate of 280kg/hr.The Diameter of duct20 can be obtained by steady-state flow simulation with a fixed pressure drop byputting ambient junctions at either end of the system and running a 1second time-basedsimulation. Varying the orifice diameter will produce different mass flow rates and we can target thedesired flow rate with the prescribed pressure drop. To understand this setup, see:.\Ricardo\WAVE\8.0\examples\engine\TUT_si\Air_Filter_CalibrationIn this case, the orifice diameter of 140.37 [mm] provides for a 1.25 kPa pressure drop at 280 kg/hrmass flow of air. Massless ducts need only to have Left and Right Diameters defined (these mustbe equal!) and the Overall Length should be set to 0. No other parameters need be set. Whencompleted, the massless Duct Panel should appear as in Figure 8.

Figure 8: Massless Duct Panel

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Click on the Save button in the toolbar

to save the file.

Proceed to Step 3 - The Throttle Body

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SI Tutorial, Phase 4 - Adding the Intake

System and Creating Animations inWavePostStep 3 - The Throttle BodyIn this step, we will add a throttle body, represented as an orifice containing a butterflyvalve. Although this tutorial won't do so, this common practice allows for the engine load to be variedbetween cases by changing the open area of the throttle body.

3.1 The Basic Geometry

The schematic of the throttle body geometry is shown in Figure 1. In WaveBuild, we will model thisgeometry as two ducts connected in the middle using a throttle valve junction. The throttle valvejunction will represent the throttle blade.

Figure 1: Throttle Body Schematic

Place the required junctions on the canvas and connect with ducts as shown in Figure 2, startingwith the final orifice junction of the zip tube. Edit both ducts to have Overall Lengths of 50 [mm]and constant Diameters of 60[mm]. Remember to set the Discretization Length to 35 [mm] andthe Initial Conditions to the standard of 1 [bar] Pressure and 300 [K] Initial Fluid and WallTemperatures.

Figure 2: WaveBuild Throttle Body

3.2 Defining the Butterfly Valve

The throttle valve junction represents an instance of a butterfly valve type, as defined in the Model >Valves list. In order to use it, we must first define the butterfly valve. Click on the Valves menuitem in the Model pull-down menu. Click on the Add button in the Valve List and selectthe Butterfly valve type, then click on the OK button to open the Butterfly Valve Editor panel. Set theBore Diameter to 60 [mm] and the Shaft Diameter to 5 [mm], with a Minimum Plate Angle (angle atwhich the valve sits effectively closed) of 5 [deg]. The Calculated Values section of the panel willallow you to preview the calculated geometric quantities. Use the slider bar to observe the schematicand values as the butterfly valve angle changes. When completed, the Butterfly Valve Editor panelshould appear as in Figure 3.

Figure 3: Butterfly Valve Editor

With the Forward/Reverse coefficient profile type radio button selected, click on the Edit FlowCoefficient Profiles button to open the flow coefficient profile editor panel. If you have a definedprofile as a function of angle, it should be entered here. For the purposes of this simulation we willdefine a coefficient of 0.5 at 5 deg and 1 at 85.22 deg, allowing a full sweep of realistic coefficientvalues from when the valve is closed until it is fully open. When completed, the flow coefficient profileeditor should appear as in Figure 4.

Figure 4: Throttle Discharge Coefficients

3.3 Using the Throttle Valve Junction

Double-click on the throttle valve junction on the canvas to open the Throttle Valve Junction Paneland edit the ID of the junction to THROTTLE. Select Valve Number 3 from the pull-down list and setthe Plate Angle to{THROTTLE_ANGLE} (see Figure 5). This parameterizes the throttle plate angle,allowing us to set the angle in the Constants Panel, so it can change between cases, giving loadcontrol during the simulation.

Figure 5: Throttle Valve Junction Panel

The background of the Plate Angle field will turn yellow as the constant THROTTLE_ANGLE is notyet defined. Click the OK button to save the settings and close the panel and, when queried aboutadding the constant to the constants table, click the OK button again and set the value 90 for allcases (setting it in Case #1 only is sufficient, see Figure 6). Modeling the throttle fully open assumeswe are running a full-load speed sweep.

Figure 6: Throttle Valve Constant

When completed, the intake subsystem should appear as shown in Figure 7.

Figure 7: Completed Intake Subsystem

Save your model

Click on the Save button in the toolbar

to save the file.

Proceed to Step 4 - The Intake Manifold

Show

SI Tutorial, Phase 4 - Adding the Intake

System and Creating Animations in

WavePostStep 4 - The Intake ManifoldIn this step, we will model the simple log-plenum intake manifold using more complex yjunctions. The techniques for modeling a large volume with sub-volumes and for modeling a taperedduct (bellmouth entry to intake runners) will be demonstrated.

4.1 The Basic Geometry

The schematic of the intake manifold geometry is shown in Figure 1. In WaveBuild, we will model theinlet pipe as a single duct. The plenum will be simplified and assumed cylindrical in shape (with anequivalent diameter of 110 mm). Four Complex Y-junctions will be attached together using masslessducts to represent the plenum volume. Three ducts will be used to represent each intake runner. Adischarge coefficient will be imposed for incoming flow to the first runner duct, to model the bellmouthentry.

Figure 1: Intake Manifold Schematic

The equivalent network as created in WaveBuild is shown in Figure 2. Drag and drop therequired orifice and y-junction elements onto the canvas from the Elements Tree and connect themwith ducts accordingly. Remember to follow the Left to Right convention. Start the inlet pipe of theintake manifold at the last orifice junction of the throttle body. Use four Complex Y-junctions tomodel the intake manifold plenum. These four Y-junctions will be connected using massless ducts(zero overall length).

Figure 2: WaveBuild Intake Manifold

4.2 Modeling the Plenum Sub-Volumes

Editthe duct representingtheinlettothe intake manifold.Assign Left and RightDiameters of 60 [mm] and an Overall Length of 150 [mm]. Remember to set the DiscretizationLength to 35 [mm] and the Initial Conditions to1.0 [bar] Pressure and 300 [K] InitialFluid and WallTemperatures.The Left and Right Diameters of the massless ducts should equal the equivalent diameter of the Yjunctions (which will also match the DIAB values assigned to the connections) so that there is nopressure loss due to expansion or contraction. The Y-junctions have an equivalent diameter of 110mm, so assign Left and Right Diameters of 110 [mm] to the massless ducts, alongwith 0 [mm] Overall Lengths (see Figure 3). They will appear gray on the canvas, indicating theyare massless ducts.

Figure 3: Massless Duct between Plenum Sub-Volumes

The Y-junctions should be edited to have Diameter values of 110 [mm], Volume valuesof 0.75e+006 [mm3] (3.0 L divided evenly by four), and Heat Transfer/Skin Friction Area values ofapproximately 27300 [mm2] (pi*diameter*length) as in Figure 4.

Figure 4: Y-Junctions Representing Plenum Sub-Volumes

Orient the duct connections according to the layout on the screen (see Figure 2). The DELX valuesfor the massless duct connections should be 79 [mm] (the length of each subvolume in the directionof flow through the massless ducts) and the DIAB values should be 110 [mm] (equal to the masslessduct Diameters so no expansion or contraction occurs).The DELX values for the runner connections should be 110 [mm] (distance across the subvolume inthe direction of flow into the runners). The DIAB values for the runner connections require somethought. Should the area used to calculate the DIAB value for each runner connection be themaximum area the gas can expand into in the Y-junction or the length of the entire plenum?Technically, the DIAB value should be calculated from the maximum area the gas can expandinto along the length of the single y-junction into which the duct enters. This is because any lossescaused by flow traveling along the length of the plenum will be accounted for by mass transfer fromone y-junction to the next. For our geometry, the maximum area for expansion in the direction of flowfrom the runners is equal to 110 mm * 79 mm 4 = 8690 mm 2. Thus DIAB isapproximately 105 [mm]. See Figure 5 for a representative duct orientation.

Figure 5: Duct Orientation for First Plenum Sub-Volume

Note, the pressure and flow after a sudden expansion has a greatly diminished response the largerthe expansion is. Once the DIAB value is approximately twice the diameter of the entering duct, theeffect of the expansion changes very little with further increase in DIAB. Figure 6 illustrates thiseffect.

Figure 6: DIAB Sensitivity Illustration

4.3 Modeling the Intake Runners

Each runner, as shown in the schematic (see Figure 1), will be represented by three ducts. Editthe ducts to have the geometry represented in the schematic and remember to setthe Discretization Length to 35 [mm] and theInitial Conditions to 1 [bar] Pressure and 300 [K]Initial Fluid and Wall Temperatures.Themiddle duct foreachrunnershouldhavea 45 Bend Angle.To edit multiple ducts at the same time (junctions can also be edited in this manner, in combinationwith ducts if desired), multiple-select the items to be edited by holding the shift key and left-clicking onthe items or by drawing a box around the desired items while holding down the left mousebutton. With the desired ducts selected (highlighted in red) right-click on the white background of thecanvas and select the Edit Parameters... menu option. This will open the Duct TemplatePanel (since all selected elements are ducts) allowing fields to be set for multiple ductssimultaneously (see Figure 7 for example of setting duct geometry for all runner ducts). Only theedited input fields will be set for all selected ducts.

Figure 7: Duct Panel for setting parameters in all Runner Ducts

If more than just ducts are selected (e.g. if the orifice elements between the ducts are also selected),the Edit Parameters... context menu option will open the Parameters Panel, which allows you to setinput values for multiple elements at once, regardless of whether or not they are the same elementtype (see Figure 8 for example of setting duct geometry for all runner ducts).

The checkbox next to each entry indicates whether the value will be written to each item. Sincemultiple items are selected, no one item's given value will show up in the entry fields they will bezero by default. The zero value will not be written to the items unless the checkbox is selected (or thenumber zero is typed into the field).The first duct is shown in the schematic to have an entry (Left end) Diameter of 70 [mm] and an exit(Right end) Diameter of 40 [mm]. This creates a Taper Angle of approximately 8.5, higher than therecommended limit of 7 as discussed in this sidebar on Modeling Tapered Ducts. Moreover, theactual geometry doesn't have a constant taper it has a bellmouth entry (which has a rapid change incross-sectional area) at the beginning and then a gentle taper towards the duct end. This indicatesthat flow will most likely separate from the duct wall during reverse flow, from the valve towards theplenum, and a sudden expansion will occur creating a pressure loss.To account for this physical phenomenon, both ends (Left and Right) of the first runner duct shouldhave Diameter values of 40 [mm]. This means that during reverse flow, from the runner duct to theplenum Y-junction, it will experience a sudden expansion into the junction and the loss will beaccounted for. To accurately represent the effect of the bellmouth entry, the Disch. Coef. from theplenum junction to the runner duct should be set to a representative high value, in the range of 0.95 1.0 in the Openings panel for each Y-junction (see Figure 9).

Figure 9: Setting the Discharge Coefficient to 0.99

Connect the ends of the intake runners to the dangling port duct ends using asimple orifice junction. If desired, use control points on the middle runner ducts to representthe Bend Angle. When completed, the entire model should appear similar to Figure 10.

Figure 10: Completed Model with Intake System

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Proceed to Step 5 - Creating Animations in WavePost

Show

SI Tutorial, Phase 4 - Adding the Intake

WavePost can use time-based data to animate the network with color contours of basicdatasets. These animations can be viewed in WavePost and then saved as MPEG files for use inpresentations and reports.

5.1 Requesting Animation Data in WaveBuild

In WaveBuild, open the Output and Plotting Panel by selecting the Output and Plotting... item fromthe Simulation pull-down menu. Check the Generate Animation Data checkbox and click OK tosave the setting and close the panel (see Figure 1).Run the WAVE model by clicking on the Run Screen Mode button in the toolbar(if prompted tosave the model before running WAVE, click the OK button to save and run sequentially).

Figure 1: Requesting Animation Data

5.2 Adding Results to an Existing .wps File

Launch WavePost from WaveBuild by left-clicking in the Launch WavePost button in the WaveBuildtoolbar . This will open the .wps file named similarly to the .wvm file currently loaded inWaveBuild. Once WavePost is open, click the Open File buttonin the toolbar and openthe .wps file created in Phase 3, Comparison.wps. This WavePost session file is currently onlyreferencing results from the last model created, without the intake system added on. It should containsweep plots created during the previous phase of torque, power, etc.Click on the Add button at the bottom of the Output Files frame and select the newlycreated .wvd file for the WAVE model containing the intake system. The .wvd and .sum files for thisWAVE run will be added to the Output Files list (see Figure 2 below). A Query window will pop-upprompting whether to add curves to the existing plots using this file (see Figure 3). Click onthe Yes button and every existing plot will add data from the newly added.wvd and .sum files (ifmatching data exists in the new files). Open the Sweep Plots to view the comparison of theperformance parameters as in Figure 4.

Figure 2: WavePost Output Files Frame

Figure 3: Query to Add Data to Existing Plots

Figure 4: Data Automatically Added to Power Plot

Note that addition of the intake system has changed the predicted performance results. Power isdecreased near 3000 rpm, but increased above 4000 rpm. The positive tuning effects are morepowerful than the losses due to friction, expansion and contraction, and bends that were added in theintake system.

5.3 Creating and Saving Animations in .mpg Format

Animations can be created using time data stored in the .wvd file. In the Results Frame in the lowerleft corner of WavePost, right-click on the Animation folder under the Network Displays folder andselect the Add Animation Display... context menu item. This will open the Animation Panel and willautomatically redraw the model canvas to display the flow network as a simple scaled model; theducts and junctions are redrawn with relative diameters displayed and color contours to represent theselected variable. Use the file browser folder button to select the tut_si4_intake.wvd results file,change the name to SI4 Intake Case #1 Velocity, and select the Velocityvariable from thelist. Check the Crank Animation checkbox to display the cylinder #1 crank animation in the upperright hand corner of the canvas. Finally, type 2 in the Crank Angle field and hit the Enter key (thiswill update the Time and Number of Frames fields automatically) to create animation steps of 2 crankangle degrees. When complete, the Animation panel should appear as in Figure 5, below.

Figure 5: Completed Animation Panel

Click the OK button to close the panel.

Now, double click on the contour bar at the bottom of the canvas to open the Contour Map Panel (thiscan also be accessed via the Contour Map Settings... button on the Animation Panel). This allowsyou to edit the range and display of the color contours as drawn on the canvas. WavePost willautomatically scale the animation to use the global minimum and maximum values for the variablefound over the entire course of the animation. This may not represent what we want to observe, sowe will manually set the range. Uncheck the AUTO boxes and set the Minimum to -20 andthe Maximum to 180 and then set the Number of Interval Labels to 11. When completed, theContour Map Panel should appear as in Figure 6.

Figure 6: Completed Contour Map Panel

Use the buttons on the WavePost toolbar to play the animation. If desired, you can record theanimation to an MPEG file. Click on the record button to open the Movie Recordings SettingsPanel. Enter a name for the movie in the File text field (Velocity.mpg) and set the MPEGQuality to High (this will use more disk space but create a clearer image) as in Figure 7. Click onthe OK button and a progress bar will pop up to show the progress of the rendering process. This willtake a while to complete.

Figure 7: The Movie Recordings Settings Panel

When finished, a file with the name as given above will be created in the working directory. It shouldappear similar to the animation below (right-click on the animation and select Play to repeat).

Save your file

Click on the Save button in the toolbar

to save the updated Comparison.wps file.

SI Tutorial, Phase 5 - Adding the Exhaust

System and Creating Spatial Plots inWavePostThe exhaust system consists of an exhaust manifold, close-coupled catalytic converter, resonator(concentric-tube silencer), and flow-reversal style muffler. All of these parts will be modeled inWaveBuild to create the exhaust system with appropriate restrictions.

Phase 5 Steps

Optional Starting Point:

1 The ExhaustManifold2 The CatalyticConverter3 The Resonator(Silencer)4 The ComplexMuffler5 CreatingSpatial Plots inWavePost

With these five steps, our model will have a complete exhaust system that is representative of a realengine. Each part of the system will be discussed and modeling practices examined. Spatial Plotswill be created in WavePost for reporting and data analysis.

Show

SI Tutorial, Phase 5 - Adding the Exhaust

System and Creating Spatial Plots inWavePostStep 1 - The Exhaust ManifoldThe exhaust manifold consists of runners with a simple 4-1 collector. The collector is attacheddirectly to a close-coupled catalytic converter (modeled in Step 2). The manifold can easily becreated using techniques learned while modeling the intake system.

1.1 Detaching the Exhaust Ambient Junction

Before performing any actions, make sure the model is in Case #1.The 4-cylinder model with the intake system still has all four exhaust ports joined together at asingle Simple Y-junction. The ambient junction named Exhaust will be re-used downstream of theexhaust system as the atmospheric conditions after the complex muffler, but the Y-junction and ductcreated for the 4-cylinder model can be selected and deleted. Highlight both the exhaustside Simple Y-junction and downstream duct (holding down the Shift key and left-clicking) and hitthe Delete key. This will leave all four exhaust port ducts dangling (see Figure 1). These willeventually be attached to the ends of the runners from the exhaust manifold.

Figure 1: Y-Junction and Downstream Duct Deleted

Middle-click and drag the ambient junction named Exhaust down to the bottom of the canvas. Thiswill serve as the end point for the exhaust system.

1.2 The Basic Geometry

The schematic of the exhaust manifold is shown in Figure 2. It can be easily modeled asthree ducts representing each exhaust runner (connected by orifice junctions) and a Complex Yjunction representing the collector. The collector is approximately spherical in shape, buta Complex Y-junction should be used as it is more flexible for tuning purposes (Simple Y-junctionsare rarely used in real modeling!). It is extremely simple to make a Complex Y-junction behaveexactly like a Simple Y-junction by using all of the defaults for Volume, Heat Transfer/Skin FrictionArea, and DELX/DIAB settings.

Figure 2: Exhaust manifold schematic

Using the Elements Tree, place all of the required junctions and then draw the required ducts asshown in Figure 3. Connect the dangling ducts from the exhaust ports to the newlycreated orifice junctions. Remember to create a hanging duct leaving the collector Y-junction torepresent the connection with the close-coupled catalytic converter.

Figure 3: Exhaust manifold flow elements in WaveBuild

Define all the ducts using the values shown in the schematic. Remember to use 40 [mm] forthe DiscretizationLength andsetthe InitialConditions toa Pressure of 1.05 [bar], Fluid Temperature of 1100 [K], and Wall Temperature of 750 [K].

1.3 Defining the Collector and Catalyst Connection

The hanging duct that will be connected to the close-coupled catalytic converter can beassigned Left and Right Diameters of 76 [mm] and an Overall Length of 0 [mm] (i.e. it isa massless duct). This will approximately model a direct connection between the collector volumeand the entry to the catalytic converter.Define the Y-junction representing the collector using the values shown in the schematic. Oncethe Diameter of 80 [mm] has been entered, click on the auto-calculate buttonsto fill inthe Volume and Heat Transfer/Skin Friction Area fields automatically. The Wall Temperature ofthe collector should be higher than the runners. Assign similar initial conditions as the runners, butuse a Wall Temperature of 900 [K]. When completed, the Y-junction Panel for the collector shouldappear as in Figure 4.

Figure 4: Collector Y-Junction Panel

Orient the ducts as they are displayed in the schematic in Figure 1. Orient the masslessduct leaving the collector to be facing down, out of the plane of the runners, as shown in Figure 5.

Figure 5: Collector Duct Orientation

When completed, the model should appear as in Figure 6.

Figure 6: Model with Completed Manifold

Save your model

Select the Save As... option from the File pull-down menu and give the model a new name, suchas tut_si4_exhaust.wvm. Saving this file and running it with a different name will allowcomparison of results to the models built and analyzed earlier.

Proceed to Step 2 - The Catalytic Converter

Show

SI Tutorial, Phase 5 - Adding the Exhaust

System and Creating Spatial Plots inWavePostStep 2 - The Catalytic ConverterThe catalytic converter consists of entry and exit cones that will be modeled using volumes and abrick, which can be modeled using a catalyst duct. The catalyst duct allows the user to input typicalcatalyst measures, like cell density, to represent the geometry of the brick.

Example Input File:

2.1 The Basic Geometry

The schematic of the catalytic converter is shown in Figure 1. In WaveBuild, the entry and exit conescan be modeled using Complex Y-junctions and the catalyst brick can be modeled using a singleCatalyst Duct connecting the two junctions. Drag and drop the required elements onto the canvasand connect them. Don't forget to attach the dangling end of the massless duct created with theexhaust manifold to the Y-junction representing the entry cone. See Figure 2.

Figure 1: Catalytic Convert Schematic

Figure 2: Required Junctions and Duct

2.2 The Entry and Exit Cones

The entry and exit cones of the catalytic converter are modeled using complex Y-junctions in order toaccount for the pressure loss due to sudden expansion of the gas. The taper angle in these conestypically far exceeds the recommended maximum of 7, so using a duct to model the entry/exit coneswon't capture the pressure loss due to sudden expansion (see sidebar on Modeling Tapered Ducts).Double-click on the entry and exit cone Y-junctions and edit their settings to reflect the informationgiven in the schematic. The Diameters provided are the area-weighted average diameters,the Volumes and Heat Transfer/Skin Friction Areas are taken from solid-modeling software(CAD).Setthe InitialConditions tobe 1.05 [bar] Pressure, 1100 [K] Temperature,and 900 [K] Wall Temperature (see Figure 3).

Figure 3: Entry Cone Y-Junction Panel

Orient the duct connections to be directly across from each other for each Y-junction. The DELXvalues for both connections should be the length of the cone (50 [mm] for both junctions) whilethe DIAB value can be left as the default value for now, identical to the junction diametersetting: 90.2 [mm] for the entry cone and 76.4 [mm] for the exit cone. Set a Disch. Coeff. of 0.95 forboth the entrance and exit connections of the catalyst to account for the tapered cone geometry(see Figure 4).

Figure 4: Catalyst Duct Orientation

2.3 The Brick as a Catalyst Duct

The catalyst brick itself is modeled using a single Catalyst Duct which will actually only represent onechannel through the brick but creates a number of identical channels to represent the entirebrick. The Catalyst Duct is simply an element which allows input of basic geometric parameters of athe brick in order to describe the single flow channel.Figure 5 shows the method used to calculate the diameter of a single catalyst brick channel and thenumber of identical channels. It assumes that all channels are square in shape. Given the geometryof the brick, the catalyst duct should be specified to have a Cross Sectional Area of 7854 [mm2],a Perimeter of 314.59 [mm], a Cell Wall Thickness of 4 [mil], and a Cell Density of 600 [1/in2].

Figure 5: Calculating Catalyst Geometry

The Overall Length should be 80 [mm] as shown in Figure 1 and remember to setthe Discretization Length to 40 [mm]. Using the formula shown in Figure 5, the Cell Count shouldbe equal to 7304 and the Cell Diameter(single channel) should be 1.055 [mm], as shown in Figure 6.

Figure 6: Catalyst Brick Geometry

Edit the neighboring Y-junctions representing the entry and exit cones and set the DIAB value forthe catalyst duct connection to be 1.17 [mm] (this represents the expansion diameter for a singlechannel entering the volume).A common practice when modeling Catalytic Converters in steady-state, if test data is available, is toset the brick Wall Temperature to match the temperature of the gas on the downstream side of thecatalyst (from the test data) and then set the Heat Transfer Multiplier to a high value, suchas 5. This ensures that the gas temperature leaving the brick matches the calibration data.Edit the duct settings and click on the Coefficients tab to set the Heat Transfer value to 5. On theInitial Conditions tab, set the Pressure to 1.05 [bar], the Fluid Temperature to 1100 [K], and the WallTemperature to a constant named {CAT_TEMP}. When prompted to add CAT_TEMP to theConstants Table, click Yes and enter the values as shown in Figure 7.

Figure 7: Catalyst Brick Wall Temperatures

When completed, the model should appear as in Figure 8.

Figure 8: Model with Catalytic Converter

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Proceed to 3. The Resonator (Silencer)

Show

SI Tutorial, Phase 5 - Adding the Exhaust

System and Creating Spatial Plots inWavePostStep 3 - The Resonator (Silencer)The resonator is simply a perforated tube with a larger, concentric tube (can) around it. Theresonator acts as a muffler and dampens certain frequencies in the exhaust stream. The resonator ismodeled in WaveBuild as a series of complex y-junctions connected by massless ducts.

Chaptersections3.1 The BasicGeometry3.2 The DownPipe3.3 TheResonator

Example Input File:

3.1 The Basic Geometry

The schematic of the down pipe (from the catalytic converter) and resonator is shown in Figure 1. InWaveBuild, the down pipe can be modeled as two curved ducts and the resonator can be modeled asentry and exit ducts with Complex Y-junctions representing the entire length of the inner, perforatedduct and the surrounding can.

Figure 1: Down pipe and resonator schematic

3.2 The Down Pipe

Drag and drop two orifice elements onto the canvas as shown in Figure 2, to represent the ends ofthe ducts used to model the downpipe. Draw the ducts representing the down pipe starting from theexit cone of the catalytic converter.

Figure 2: Down pipe junctions

Enter the geometric properties as shown in the schematic in Figure 1. Include a 90 Bend Angle foreach duct and remember to use a Discretization Length of 40 [mm]. Set the Initial Conditionsto 1.05 [bar] Pressure and1000 [K] Fluid Temperature with 800 [K] Wall Temperature. If desired,use control points to represent the bend angle on the canvas.With the down pipe modeled, the canvas should appear similar to Figure 3.

Figure 3: Down pipe ducts

3.3 The Resonator

The resonator is modeled with a short entry duct (40 mm long as shown in Figure 1), Complex Yjunctions representing the inner perforated duct and the surrounding can, and a short exit duct. Thecompleted WaveBuild representation of the resonator appears in Figure 4.

Figure 4: Resonator representation

The number of consecutive Complex Y-junctions to use can be determined by dividing the total lengthof the can (300 mm) by the exhaust discretization size (40 mm). The results in 7 Complex Yjunctions used in series to represent the inner perforated duct and 7 more used to represent thesurrounding can. The easiest method for building this resonator model is to build and define the firstComplex Y-junction for the inner duct and outer can each, and then copy/paste them 6 times.The first Y-junction representing the inner perforated duct is cylindrical -- 42.857 mm long (300mm/7)and 50 mm in Diameter. This means it has a Volume of 84149.8 [mm3] The Heat Transfer/SkinFriction Area can be calculated from the area of the pipe minus the area of the perforates connectingto the outer can. The area of the perforated section of pipe is 47123.89 mm 2. The total area of theperforates account for 20057.5 mm 2. Assuming the perforates are evenly distributed along the entirelength of the pipe, we can calculate the surface area of a single Y-junction as 1/7th of the total surfacearea. Thus, the total Heat Transfer/Skin Friction Area for the single Y-junction is 3866.63 [mm2]. Setthe InitialConditions to 1.05 [bar] Pressure, 900 [K] FluidTemperature,and 700 [K] WallTemperature. The Y-junction panel and pipe orientations should appear as in Figures 5 and 6.

Figure 5: Inner, perforated pipe y-junction

Figure 6: Inner, perforated pipe y-junction orientation

The first Y-junction representing the outer can is cylindrical as well, with the volume representing theinner duct subtracted (don't forget to include the 1 mm thickness of the tube wall). This creates atorus, or doughnut-shaped volume, with an equivalent Diameter of 108.15 [mm].Theresulting Volume is 393686.4 [mm3] The Heat Transfer/Skin Friction Area of the entire outer can,including the end-caps can be averaged over all seven Y-junctions, and is 18781.3 [mm2]. Setthe InitialConditions to 1.05 [bar] Pressure, 800 [K] FluidTemperature,and 600 [K] WallTemperature. The Y-junction panel and pipe orientations should appear as in Figure 7 and 8.

Figure 7: Outer can y-junction

Figure 8: Outer can y-junction orientation

Copy/paste the two Y-junctions to create seven of each, in series as shown in the figure below. Allofthe Y-Junctions representingtheinner,perforatedpipeshouldbeconnectedby massless ducts with Diameters of 50 [mm]. All of the Y-junctions representing the outer canshould be connected by massless ducts with Diameters of 108.15 [mm]. And each inner,perforated pipe Y-junction should be connected to the adjacent outer can Y-junction byamassless duct whichrepresentstheperforates,witha Diameter of 11.3 [mm]anda Count of 28.57 (=200/7, assuming they are evenly distributed).

Figure 9: Connectivity using massless ducts

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Proceed to Step 4 - The Complex Muffler

Show

SI Tutorial, Phase 5 - Adding the Exhaust

System and Creating Spatial Plots inWavePostStep 4 - The Complex Muffler (Optional)The complex muffler is a complicated portion of any WAVE model. It usually consists of multiplepipes, possibly perforated, passing through internal baffles within a large complex-shaped volume. Itmay have packing material made of rock wool or fiberglass in portions of the volume, used to dampenacoustic transmissions.Due to the complexity and tediousness of modeling this muffler, it is NOT mandatory for you to buildit, but it is recommended that you understand the idea behind it and appreciate the need for a routineengineering tool to automatically mesh and generate a WAVE input file for such complexcomponents.Fortunately, Ricardo Software has developed such a tool namedWaveBuild3D. WaveBuild3D is especially useful for auto-meshing intake and exhaust componentsfor NVH applications. For more information about this tool, please contact your Ricardo SoftwareSales representative at (734) 394-3860 or via email at RS_Sales@ricardo.com.

4.1 The Basic Geometry

The schematic of the mid-pipe and complex muffler is shown in Figure 1. In WaveBuild, the twosegments that represent the mid-pipe can be modeled simply as two ducts, starting from the orificejunction at the end of the resonator. The complex muffler will be modeled as a series of inter-

Figure 1: Mid-Pipe and Complex Muffler Schematic

4.2 The Mid-Pipe

Drag and drop two orifice elements onto the canvas as shown in Figure 2, to represent the ends ofthe ducts used to model the mid-pipe. Draw the ducts representing the mid-pipe starting fromthe orifice junction at the exit of the resonator.

Figure 2: Mid-Pipe Junctions

Enter the geometric properties as shown in the schematic in Figure 1. Include a 90 Bend Angle forthe first duct and remember to use a Discretization Length of 40 [mm]. Set the InitialConditions to 1.05 [bar] Pressure and800 [K] Fluid Temperature with 600 [K] WallTemperature. If desired, use control points to represent the bend angle on the canvas.With the mid-pipe modeled, the canvas should appear similar to Figure 3.

Figure 3: Mid-Pipe Ducts

4.3 Modeling the Muffler in Quasi-2D

Because the muffler is such a large and complex volume, the three internal chambers whichphysically divide the muffler vertically, as shown in the schematic, should be sub-divided and modeledwith multiple Complex Y-junctions. Each section of perforated pipe will also have to berepresented by Complex Y-junctions attached to the surrounding volume(s) with multi-countmassless ducts to represent the perforates, as in the resonator. The level of refinement is up tothe user and what kind of results they desire: for performance, simple Quasi-2D meshing may besufficient but for acoustics, detailed Quasi-3D meshing should be performed.We refer to meshing in WAVE as "Quasi" meshing as it is not identical to full-scale 3-D CFD but canapproximate the same results. Quasi-2D meshing (Box A in Figure 4) is sub-division of volumes in 2axial directions (X and Y, in this case) and ignoring the division in the 3rd direction (Z axis). Quasi-3Dmeshing (Box B in Figure 4) is sub-dividing volumes in all 3 axial directions. The number of subvolumes increases dramatically between Quasi-2D and Quasi-3D meshing!

Figure 4: Modeling in Multiple Dimensions

The complexity of this connectivity of Y-junctions, massless ducts, and normal ducts has no uniquelycorrect design and different designers might end up with different connectivity matrices for this samemuffler. Also, this modeling work has no real engineering value, it's only routine work that could to beautomated! It is expensive and tedious for you, the engineer, to spend your time on such laborioustasks. For this reason, Ricardo Software introduced WaveBuild3D as an auto-mesher for largecomponents in the intake and exhaust systems using a solid-modeling interface to represent thegeometry. The table below shows a comparison for different mesh matrix sizes vs. pre-processingtime of manual meshing (by you the user) and WaveBuild3D (computer program auto-meshing).* Based on average time an engineer spends to complete one complex Y-junction input = 6 minutes** Based on meshing using Intel Core 2 Duo T7600

# of Subvolumes(Matrix Size)

Meshing Type2D/3D

# of RepeatedTasks

EngineerMinutes*

WaveBuild3DMinutes**

3x3

2D

18

108

0.03

3x3x3

3D

54

324

0.05

9x9x9

3D

1458

8748

0.37

15 x 15 x 15

3D

6750

40500

0.83

nxnxn

3D

2 x n3

2 x n3 x 6

It is left to you, the new WAVE user, to complete modeling the muffler. At this point there is nothingnew to learn. All that needs to be done is repeating the geometric and duct orientation input manytimes to model the muffler as a network of ducts, massless ducts, and Complex Y-junctions.The muffler is shown in WaveBuild3D in Figure 5 and the corresponding WAVE mesh is shownin Figure 6.

Figure 5: Muffler in WaveBuild3D

Figure 6: Muffler mesh from WaveBuild3D

The WaveBuild3D tool creates portions of WAVE models known as Components. Any WaveBuild3Dcomponent can be used in any WAVE model, regardless of whether or not the user has aWaveBuild3D license. This muffler component is shipped as an example model. To add it to themodel, expand the Tags branch under the Components branch of the Elements tree. Drag and dropthe SI_Muffler component onto the canvas and connect it to the model by attaching the last duct ofthe mid pipe (the last orifice element can be deleted, as it is no longer necessary) to the inletconnection point of the component. Connect the outlet connection point of the muffler component tothe Exhaust ambient using a duct with 50 [mm] diameters and an overall length of 40 [mm] (use initialconditions similar to the mid-pipe).When finished, the model should appear similar to Figure 7.

Figure 7: Completed Model in WaveBuild

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Proceed to Step 5 - Creating Spatial Plots in WavePost

Show

SI Tutorial, Phase 5 - Adding the Exhaust

System and Creating Spatial Plots inWavePostStep 5 - Creating Spatial Plots in WavePostWavePost can use time-based data to create plots of scalar/vector quantities along a length of thenetwork to observe traveling pressure waves, temperature profiles, etc. These spatial plots can beanimated to observe the temporal change in WavePost and saved as .mpg files for use inpresentations and reports.

Chapter sections Example Input File:

Example Output File:

.\Ricardo\WAVE\8.0\examples\engine\TUT_si\tut_si4_intake.wps

5.1 Creating Spatial Plots in WavePost

Run the WAVE model by clicking on the Run Screen Mode button in the toolbar(if prompted tosave the model before running WAVE, click the OK button to save and run sequentially).Launch WavePost from WaveBuild by clicking in the Launch WavePost button in the WaveBuildtoolbar . This will open the.wps file named similarly to .wvm currently loaded in WaveBuild. OnceWavePost is open, click the Open File buttonin the toolbar and open the .wps file createdin Phase 3, Comparison.wps. This WavePost session file is currently referencing results from the4-cylinder model without intake/exhaust (tut_si4) and from the four-cylinder model with intake only(tut_si4_intake). It should contain sweep plots created during the in Phase 3 of torque, power,etc.Click on the Add button at the bottom of the Output Files frame and select the newlycreated .wvd file for the WAVE model containing both the intake and exhaust systems(tut_si4_exhaust). The .wvd and .sum files for this WAVE run will be added to the OutputFiles list. A Query window will pop-up prompting whether to add curves to the existing plots usingthis file. Click on the Yes button and every existing plot will add data from the newlyadded.wvd and .sum files (if matching data exists in the new files). Open the Sweep Plots to viewthe comparison of the performance parameters.On the Canvas of the WavePost GUI, use the Shift+Left Click to multiple-selectthe ducts and junctions along the intake runner to the cyl1 junction (see Figure 1). Right-click onone of the ducts/junctions in the highlighted group and select the "Add Spatial Plot > Basic >Pressure" menu item, as shown in Figure 2.

Figure 1: Ducts and Junctions for Spatial Plot

Figure 2: Adding a spatial plot via the context menu

A Spatial Plot of the pressure along this path will be automatically created, showing a scaled view ofthe ducts/junctions along the path and the pressure profile in those ducts/junctions on the sameplot (see Figure 3). Therepresentation of the ducts/junctions can be moved using the middlemouse button or removed from the plot altogether by double-clicking on it and de-selectingthe Display Scale View option, where the crank animation can also be displayed (also accessiblefrom the Tools > Display pull-down menu item).

Figure 3: Spatial Plot Display Panel

Figure 4: Spatial Plot of Pressure in Runner 1

5.2 Animating Spatial Plots

Spatial Plots can be animated just like canvas displays of network variables, as demonstratedin Phase 4. Simply open the Animation Panel by selecting the Animation... menu option fromthe Tools pull-down menu (seeFigure 5). The animation can be played or recorded to a MPEG filefor use in reports/presentations. The Time Offset can be set to change the starting point of theanimation, allowing multiple spatial plots to be shown in/out of phase.

Figure 5: Spatial Plot Animation Panel

The Animated Spatial Plot should appear as the video at the bottom of the page.

Save your file

Click on the Save button in the toolbar

to save the updated Comparison.wps file.

CONGRATULATIONS!The 4-cylinder model is complete! All of the basic principles in WAVE modeling have been introducedand explained as well as the basic methods of building a model and post-processing thedata. Optional phases follow to elaborate on the basic principles.